the go pro is fun, but i recommend an iPhone and the app called Harry's Lap Timer.
It has 1000's of tracks, follows you in GPS, makes nice video with telemetry overlay, and has a "track timer" mode to show you segment times, predicted laps/etc.
IMG 1331 - YouTube
i plan to run two iPhone's next year. One taking video and one running the "track timer". I'll wait a few more weeks to get the iPhone5 though