The Nook Simple Touch can be rooted. I found it to be a little bit unstable, but YMMV.
http://nooktalk.net/blog/reliable-way-to-root-nook-simple-to...
Simple Touch readers should be dirt-cheap.
http://nooktalk.net/blog/reliable-way-to-root-nook-simple-to...
Simple Touch readers should be dirt-cheap.
You can configure it such that the Nook would boot and appear as normal, but holding down a key took you to the android launcher, and you would give up the use of two (redundant) buttons of your choice to control android-specific actions like <back>, etc.
This system was limited -- at the time -- to an older version of Android with limited app support, but if your purpose is to create your own apps this shouldn't pose any problem.