FINIS has recently released the AquaPulse, an underwater heart rate monitor for swimmers which promises to be more practical than old-fashioned chest straps and watches. The device itself is attached to the goggle strap, and an infrared sensor is attached to the earlobe, measuring the heart beat by capillary activity.
The heart rate is announced by a voice which is transmitted to the inner ear using bone conduction technology. Cost for this little gadget? well worth it if it will help you win in the Olympics. An overview of the features from the press release: