I'd like to encourage you to add support for penciling, i.e. writing in multiple possible solutions to unsolved cells.

All the advanced solving techniques needed for tougher Sudoku puzzles (pointing rows, hidden triples, x-wing, swordfish, etc) require penciling, then looking for patterns in the penciled possibilities. None of the Android-based Sudoku implementations I've seen seem to support penciling, and hence seem only usable for fairly trivial puzzles.

Here's an example of a PalmOS-based Sudoku game that works very well, and allows penciling on a smaller screen than the G1 has.

http://www.scss.com.au/family/andrew/pdas/palm/myprogs/sudoku/