In order to demo the actransit_rails gem, I wrote a small transit web app, BayCrosser, that pulls updated Transbay bus schedules. (Transbay buses cross the Bay Bridge, allowing commuters from the East Bay to get into Downtown SF).
The app is designed to fit one simple role: telling you available trips for a selected Transbay bus route. I kept the app simple to focus on using the gem, and on making an app that worked quickly on mobile devices.