Can I extend my screen to another Android device?

[Chriswaterguy]

I can extend a Windows computer's screen to my Android device using an app such as TwomonAir or TwomonUSB - giving me two monitors by using the Android device as a second monitor.

But can I extend the screen of an Android device to another Android device?

(I'm planning my next purchase of a tablet or laptop/netbook, and would really like something that can run two screens.)