The breastlight is a medical gadget that allows women to examine suspicious breast lumps.
Malignant lumps have an increased blood supply to feed them so any dense areas may indicate an abnormality. Fluid filled cysts, however, will not absorb the light.I don't think they are sold in the US, but in the UK they cost £77.50.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. Come and hear Mark speak at the ALA conference in Chicago on July 1.