Android App Coin Market

I'm an android developer and i was thinking on creating an app to monitor the value of several crypto currencies. Pretty much what coinmarketcap.com does for the browser but for android, with some native niceties such as widgets, alerts, etc

Planned features
- Native app
- List of coins sorted by market cap, price, name, price change in last 24hs, etc
- Status bar alerts on prices drops/rises on specific coins
- Widget: configurable for specific coin
- Widget: with list of top X coins
- Graphs with the coins performance in several periods of time ( 24hs, 7/15 days, 1/3/6 months)

What i'm missing and most interested on asking you guys, is what kind of datasource can i use to get all this information.
I would be nice to get all this data from an API obviously, but i could parse an html site too. What alternatives do i have? What are the most reliable/known datasources for this data?

Thanks a lot!
Robert