Perfect for regular, on-the-go use (the USB charging looks ideal). The GEO.
NB : We first looked at this one in the weekly Strength & Fitness Newsletter (part of the Strength Kit). If you'd like to have it sent to you automatically (free!) each week, just add your email here.
We also discuss a number of training-related books, videos & pieces of equipment (there's a full list here). If you're looking for the books I'm checking out personally, swing by Goodreads. And to see the various ones we've recommended over the years, swing by the Strength Store.