Choosing a mobile platform
satyajit: Consider Nokia's WRT (Web RunTime) .. they have a JS based SDK (prototype, JQuery).
Join Forum Nokia to learn more about their offering, and their app store is releasing in May. LBS awareness, bground processing, JS/CSS based SDK makes it easier to develop on it. Though Nokia isn't that big in US, but has a bigger reach worldwide than iPhone/Android.
Our app is a rails app too, and I am considering writing my app for Nokia WRT. Apart from WRT, you can also write Symbian OS (C++) native apps, or Java, or Flash (our choice) apps.