The GolfSense device (suggested retail price $129) also works with an iPad and is being sold by Apple Computer outlets. GolfSense clips conveniently to the Velcro closure on your glove and since it only weighs 0.6 oz.
Best of all perhaps, it won’t interfere with your swing. The motion sensors – there are four – measure data at 1,000 times per second and provide the analysis through a wireless connection to your iPhone or iPad.
The result is a 3-D graphic showing your swing and a precise calculation of club head speed.