Groupon offers the Ion Audio Piano Apprentice for Apple iPad, iPhone, and iPod touch, model no. iCK05, for $29.99 with free shipping. (Amazon offers it for the same price.) That's the lowest total price we could find by $20, although we saw it for a buck less in June. This 25-key touch-sensitive keyboard is compatible with the 30-pin iPhone, iPod touch, and iPad. It operates on an AC adapter (not included) or four AA batteries (included). Deal ends March 9.