Bitcoin Balance Scanner is a free application on the Android Market that allows you to scan a QR code of a public Bitcoin address. This will then use the BlockChain API to lookup the current balance. History is saved to allow quick and easy lookups.
Not much more I can say about it, it's simple and to the point.
This is the product of about 4 hours of work, so it has the ability to grow based on suggestions.
Get it on the Android market:
https://play.google.com/store/apps/details?id=com.beyondem.bitcoinbalanceReddit Post:
http://www.reddit.com/r/Bitcoin/comments/1k3ws2/bitcoin_balance_scanner_scan_a_qr_code_get_the/Edit: I see the play store says it requires Android 4.0.3 and up. I will do some testing on some previous versions and try and add more support for devices.