Router Aqua app for Android is comparable to the Flow App (iOS) previously posted. Currently free in the Amazon App Market (today only!), this app provides visual spatial reasoning and visual motor challenge for your clients needs or you (this is the kind of games I really like!). In app purchases are available for more challenges.
Here is an image of the Router Aqua app:
Router app is a similar app (.99) available from the same developer provides more visual spatial reasoning activities on your Android device.
Have fun Android Appers! More for your OT eTool Kit!