I used to use my phone to record my rides, but the battery drain was killing me. Not only did I need an external battery for longer rides, even on shorter rides if my battery died I didn't have a phone.

That Garmin Edge 25 is a good deal. I picked one up for $125 from a UK web site last year. The Garmin soft chest strap is $35 or so. For $160 you get a top notch GPS unit that won't run down your phone battery. Also, the Edge 25 is tiny. I really liked that about it.