With just 3 buttons:
- Buy coins (something that streamlines buying at the exchanges).
- Send coins
- Receive coins
There are many options for Buy coins and Send coins:
-
http://en.bitcoin.it/wiki/Mobile_Payment_AppsBitcoin Spinner (Android) has a Buy coins button but that just uses BitInstant.
CoinBase is probably going to be the closes to what you are looking for. Think PayPal, with a linked bank account and where you can send a payment funded with a credit card, but uses bitcoins instead of USDs for the payment. They are a young company yet though and those methods aren't even in testing yet. It's coming.
In the meantime, combinations of services work pretty well. A mobile app wallet (e.g., Blockchain for Android + an exchange account) can be used together fairly easily.