I went ahead and wrote a python script which can extract the seed from either a backup file or from the raw wallet file (which you can only get to if your phone is rooted). Feel free to give it a try, instructions and download links are at GitHub: https://github.com/gurnec/decrypt_bitcoinj_seed. You'll of course need your backup password (if it's a wallet backup file) and your PIN, if any.

I've verified that the seed I get from the script can be used to generate the same sequence of addresses/keys as are in the app (I just went here and plugged in my seed -- obviously if you choose to do something similar with anything but a test seed, you should use an offline copy of that page).