TomTom GPS Watch
The TomTom GPS watch is an in-expensive way to ditch your iPhone for tracking runs. This will allow you to save your phone battery life, or allow you to completely ditch carrying an extra device. The reason I am mentioning this particular watch is that it can sync your runs to Runkeeper after the fact. You can set vibration alerts for various times and distances. It also includes a 10 hour battery life.
Get it on Amazon for $89.99-$99.99 (depending on color).