Using Arduino to pass data from a coin collector to android app
Here are a couple of opitions for you:

1- Bluetooth - if in close range, an HC-05 will work great.

2- Wifi - wifi can work good. It is a little more complex then bluetooth but its range can get further. For example, a Tweet can be sent each time a coin is detected.

3- GSM - it is pretty much texting. You can make it so the coin collector texts you or someone there is a coin.

All of these solutions work great with the MIT app creator. It makes the data you receive much easier to process.