I don't see a problem with it. I say put it out there and see if it's of interest to the HN clan. By inhibiting yourself, you're only depriving yourself of an audience who might be genuinely interested.
That's a great app idea but that bothers me to pay for suggestion cards. I understand there is work behing the hood for the iPhone application but still. Does anyone know a website with some free example cards decks to print out ?