What site or app for biofeedback can you recommended that's not too pricey?

Try this one . . . "deep sleep" by andrew johnson. Now get a comfy reclining chair, darken the room, and block out the rest of the world. This app is really hypno therapy rather than purely biofeedback, but it's probably the type people need for dealing with stress. This same individual makes similar apps for other purposes.
Biofeedback site. One biofeedback site that has reputable equipment and interactive games in the $400 to $500 range is www.Wilddivine.Com. Another site that has a wide variety of equipment, including simple skin temperature and gsr devices, is www.Bio-medical.Com.