For me, the coolest feature would be to allow on-device development -- have a BASIC interpreter running on the phone to let us create programs on-the-go.
Then, when you get home, move the code to the computer and use Basic4android to compile it to an android executable.
After all -- an interpreter is the root of BASIC
For me, I wouldn't care if the phone interpreter had any kind of visual designer. Something that would let me open a "something.bas" text file with my BASIC code and run it would be awesome.