A function generator is generally considered a bench top test instrument....but such functionality pastered into a microcontroller could be adapted to some pretty interesting applications. Take a peek at this application note from Cygnal (Now Silicon Laboratories):

http://www.silabs.com/products/pdf/an123rev1_1.pdf

Kindly provided C code is here:

http://www.silabs.com/products/...n123sw.zip

Michael Karas