Just as the title says.
Create an app and release it on the android market for free. Anyone wanting to buy bitcoins could download the app, enter their bitcoin receiving address, pay for them using an in-app purchase and the app developer sends the bitcoins to the supplied address. Not sure if you can dynamically change the price in an in-app purchase but if not there could be a fixed purchase price in $ or whatever and the number of bitcoins sent would vary depending on the exchange rate. The seller would add at least a 30% premium to cover the 30% transaction fee charged by Google but I think there could still be a demand even with this premium due to the convenience.
Relevant links: https://www.google.com/support/androidmarket/developer/bin/answer.py?&&answer=1153481 http://developer.android.com/guide/market/billing/billing_overview.html