I'm building an Android application that can take pictures and videos. I need to build a RESTful web service using Ruby on Rails. If I click send option in my application those pictures and videos should get uploaded to web service. Here are my concerns:
For logging in, you could pull up the login page on the mobile device. This will be the easier route. Just make sure the page is mobile friendly and responsive. Use a WebView to do so.
Using android with a rails RESTful api is no different than interacting with any other RESTful interface. Check out AndroidAsync. This will help with the HTTP communication.