OurCar: What I learned making an app for my family (opens in new tab)

Oh man! I made an app for my family too. They have an antiques/book selling business on eBay so I made an app for them to actually keep track of things as they buy them.

That was where their process was breaking down - When did we buy this? How much was it? The sort of things that are semi-difficult to keep track of when you're going to A LOT of estate sales and then basically need to enter all the stuff into a spreadsheet when you get home.

So the concept was - take pics and enter simple data as you're out and about and then export the data when you get home.

I ended up going way down some deep rabbit holes because I didn't want to host any data (my goal was to actual release the app and hosting people's shopping trips wasn't something I wanted to take on).

So it's all local storage and for sharing between family members I ended up embedding the data in a pdf that you can send in a text and then import - so if x people are at the same sale they can all add to the same "trip" at the same time and then combine the trip when they're all finished shopping.

So image and data optimization were big concerns since it's all on your phone until you export it/delete the trip.

I was a fun process until it wasn't :P

I did end up getting to 1.0 and shipping to the app store, which was really my goal -> make an app and go all the way through the process. So in that way it was a success.

Hi HN! OP here. This is my first post and I'm very grateful to see it on the front page. This app was a lot of fun to build, and I really enjoyed putting together the writeup. I've been very inspired by the other stories shared here to write my own, so seeing the comments has been very validating.

I guess I'll be around answering questions and comments as I see them. Thanks for reading and responding.

Most of the friction I’ve hit with tiny household setups isn’t “what does the gauge say”—it’s who last updated shared state (trips, refuels, keys) and whether the next driver can rely on it. A rough UI everyone actually opens can beat a neat paper log maintained by one person.

The pencil‑and‑notepad takes make sense once the ritual is already mutual; the failure mode I see is partial adherence, where informal notes silently diverge. A purpose‑built helper can be the workflow, not only the record of it.

I’ve shipped a couple of relatives‑only gadgets; “it worked” usually meant routines lined up across people, not that the tech was flashy.

Fun project. The article is a bit light on details. I find it astonishing that a project like this runs into performance issues. I would have liked to learn more about what these resource-constrained widgets looked like, what they did, and what caused the performance issues.

For years the family joke has been that when we take a family picture we need to take 5 because I will inevitably have my eyes closed in the first 4.

So I made an IOS app just for us that does face detection and won't take the actual photo until all of the detected faces have their eyes open.

Manual data entry is just too unreliable and time-consuming. I don't see how this could work short of integrating OBD-II fuel consumption data combined with some sort of presence tracking.

Great writeup and also a great example of where LLMs can step in to help fill the gaps in areas where you don't have as much skill or interest. For instance, your wife used ChatGPT to come up with a name and you used AI to generate the admin flows that you weren't interested in building.

Sounds like Flutter was a good technology choice too, given its flexibility across platforms. As a designer, I know how frustrating it can be that the Google and Apple interface guidelines aren't too prescriptive but patterns vary so much across domains, that it's better to do what you did and evaluate what others do to solve similar problems. Great work!

Good example of over-engineering.

This could be easily solved with a pencil and notepad.

We own a Subaru, and the app has all sorts of data in it: the car's current location, the odometer reading, and fuel status, sort of - it only displays the "until empty" distance, and the average MPG. I'm surprised it doesn't show even an estimate of how much gasoline is in it.

So if I were to do this, I'd find a way to read that data somehow, and then I'd just need to know who was driving. (Which, as someone pointed out, I'd probably do with some sort of RFID tag on everyone's keys.)

But yeah, the manual entry part would absolutely be the biggest drag here.

Plenty of comments about using an LLM to assist with this, and I was happy to be able to read about a learning experience where the stakes were pretty low and the feedback loop pretty tight. Thanks for writing it up; for me, it reminds me that some of the use cases where an LLM might be an efficient tool are also the places where it can be wise to take the opportunity to learn and sharpen new skills.

Hmm an app where you can count the users on your fingers, and where it's not a big deal if it's slightly wrong.

Safe to LLM generate it, unless you want to learn something in the process, in which case do whatever parts you want to learn about manually.

Had an 100% generated app with one user - me - on my phone's home screen since some time last year.

also fwiw for small things like this, unless you want to really learn image recognition, just send the image to gemini-flash-3 or something. Sure it's 0.5-1s latency, still faster than entering it manually and it's pretty cheap, I'd reckon it's under the free tier at least for you and your family.

Interesting, was actually planning on setting up a carshare for our cul-de-sac in Honolulu. This is a great reference, thanks for sharing.

I’m surprised the author went for native apps rather than a PWA for this use

Honestly, this is kind of the sweet spot for LLM-built apps.

Small thing, used by a few people, solves one annoying problem, and nobody really cares if it’s not “proper software”.

Clearly the car was the Top Gear KIA Cee'd and you must be The Stig.

We all start pet projects with the tools we know, to learn new tools along the way. Sometimes you have a nail and the hammer is the right tool for the job. However, why use just the hammer when you can just download the whole Snap On tool inventory for the same price, in both metric and weird American units?

From your write up, I felt that the frameworks were not helping. A HTML file served as a PWA would provide everything needed, without the need to go through the hoops of app stores and debugging with those fancy AI things. To open the page an NFC sticker in the car could work.

What I am saying is 'Keep It Simple'. Oh, and get a bicycle! Most of the world uses 'active travel' for most journeys, only in America is 'active travel' effectively banned by zoning laws and whatnot. Maybe v2 of the app could be all about car dependency, which should be regarded as a chronic disease, with some of the methods used by 'quit smoking' apps to keep users motivated to ride a bicycle or walk, rather than get in the tin coffin.

Integrate an OBDii dongle with Bluetooth and have the app read it from there.

Next: "How I made one whole website to host one HN-featured blog post"

Best family app to me is home assistant.

It's so powerful and you can build so many custom UIs on it.

I started it for smart home automations but on daily basis I use it more for managing tasks,scheduling reminders.

And with Claude code remote even my not so technical wife uses it to build her tiny utility apps.

Cool, glad you had fun building it.

Notably, the only parts of this that could not have been done by a well configured agent in a weekend with SOTA today is the futzing with app stores and the UX iterations.

wow... so much yak shaving, including priceless bits like "sat with ChatGPT for a bit [...] we came up with OurCar" (I mean... how original is that, clearly powerful datacenters computing over a dump of the Internet was needed), I'm impressed.

All this to avoid doing one subtraction (km before, km now) then multiplication (result times average litter/km) in your head.

That's a LOT of effort to be lazy.