It’s not cool anymore but I use PHP and MySQL with a $5/mo inmotionhosting account. This is after I decided to not take on the overhead of native with multiple code base and App Store deployments. Good ol’ webapp it is.
However every single day I do wish there was a solution for my webapp to get access to contacts on the phone and of course notifications. It would have been a game changer given the nature of the product. Currently it is a world of compromises for hobby developers (shameless plug: http://ping3.com)