First of all, thank you all for your unvaluable help.
I work for a little company wich main target is helping and improving the life of disabled and elderly people. (www.jobaccommodation.es
our intention is to update the web in english, sorry about that...
A couple of associations proposed us to develop an accesible ereader for people with low mobility (as cerebral paralysis, ..) or low vision. Then we decided to design our own ereader with a usable graphic interface and a remote controller (a simplified bluetooth keyboard, for example) to control it. That's the main idea.
We have experience in C, C++ and Java languages and we have tested the Android SDK. We are Linux users but none of us have experience in building the OS itself.
I hope you could better now understand our situation. Thank you again for your help!