How do you find out how much data has been transferred over Wifi, 3G or EDGE on Android?

I'm trying to write an Android widget that shows how much data has b开发者_如何转开发een transferred over 3G/WIFI/EDGE but I can't seem to find the API call, even though other widgets do this. Does anyone know what the API calls are to get the data usage?

Ah, found it, android.net.TrafficStats.