The RP4900 Portable USB Power Source is a great product for taking along to give your portables a little extra juice. I personally have used one of these (from a competitor) for several months now and it's an excellent way to recharge or extend the life of your portables when you're on a particularly long trip or will be away without power for an extended period of time. The Tek4 4V system works well and will charge just about anything that can run from a USB power source. It's lightweight and will fit into just about any carry-on bag, camera case or even a purse. The kit doesn't come with a battery so it's assuming you already own at least one other Tek4 product or you're willing to pony up the additional $25 for a battery and Standard Charger.

If you factor in the battery, this places the value of this product smack dab in the middle of the pack, though - and this is key - for $20 existing Tek4 users will find it a better-than-average value.