1. Great Noise cancelling headphones are very expensive, because only a rare few companies has managed to do the r&d to create great noise cancellation

But if there we're affordable headphones that are software programmable and act as an app store for noise cancellation algorithms, that would definetly reduce the price.

2. One of the ideal ways to recieve ecommerce packages is on your car's trunk. It's possible to build a smart lock for your car that enables the delivery guy to drop packages.

The hard part is making it cheap, making installation cheap, and designing a rapidly growing business model that grows rapidly.

3. Many restaurant use a combi-ovens to reheat frozen food with great results. Combi ovens are now starting to become cheap($300), most of them for the home.

But what about the workplace , where for some places, frozen food may be a good alternative to restaurant ordering(it may be cheaper, for example), but that will require an affordable multi-meal oven, which doesn't exist yet ?

4. Apache Isis is a great, rapid , domain driven framework for business app development. But it's quite complex. There may an opportunity in synmplifying it and introdcuing it to new users. Maybe in a service based form.