The Camera for the QR code scanning.  Usb storage to store the wallet data and block data (not the full block chain).  Bluetooth for transactions over bluetooth. Full network access for lots of things. Like the block chain headers,transactions, exchange information (when it is updated) etc.

If your suspicious, which would be perfectly understandable being a security conscious person myself, feel free to go through the source and compile the apk from that. It is available on github, although I still need to update the build instructions.

https://github.com/digibyte/DigiByteAndroid