I think this app is less about mining and more about payments on the go.

Word. I imagine it would take my old HTC Magic about 9 years to process the block chain. Also even though I wouldn't keep much BTC in this wallet, I don't like the idea of just storing it 'in the cloud' or whatever.

We actually prepackage a recent blockchain with the app when you download it. So it only needs to udpate the last bit the first time you run it (< 1 minute over wifi). After that future updates are near instant (a few seconds) over 3G or WiFi.

Brilliant software... have been waiting for this.

One obvious question: is there anything to prevent someone from repackaging this, as it's open source, and modifying it to rob folks?

No. Just like any other open source software. It's also possible that people who download the apk from the Android Market Place are getting a backdoored version of the software.

This relies on trust.

Does anyone remember Paypal updating their iPhone app last year to do SSL certificate verification because up until that point it was trivially MITM'able?

Thanks for explaining all of this in the comments. I was wondering all of these things...