IAP (in-app purchases) are becoming a real problem on Android games. Here are some techniques that can help work around them.
Almost all of these require root.
get in-app-purchases for free
fast-forward the system clock
If you're unsure how to use these, download Cheat Engine and go through the tutorial. While there are slight differences between RAM cheat programs, the general concept is the same, and it's a little easier to learn how to do this on a PC.
backup and restore game data
This is sort of like save-states in Nintendo emulators, but you have to exit your game before you can backup/restore.
- limited game support
- supports any app
modified game binaries
websites and forums