Here is a pair of smart goggles that can help you improve as a swimmer. The Zwim is a Google Glass like device with a HUD that shows your lap time, heart rate, and other relevant info. It syncs to your smartphone, so you can make sense of the data.
The Zwim uses an optical heart rate sensor to monitor your performance. It is waterproof to 30 meters. The battery life lasts 4 hours.