http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sec...
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sec...
martythemaniak is right - build it first, worry about patents later.
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sec...
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sec...