Android app for tactics training

Here's an Android free app with over 15,000 tactics puzzles and 6 levels of difficulty:

1-IdeaTactics
This application needs internet connection, without an internet connection the app doesn't work because all problems are on internet and are downloaded one at a time.

2-iChess
This application don't needs internet connection it works off-line.

3-Chess Puzzles

not free but very very cheep