I have been looking at the same device and I think it has a 480mah battery which is ok for a lr atty. I would not plug it into my computer because I would not want to risk a malfunction with the device that would harm my computer. I would use a wall wart type AC to USB adapter that puts out at least 500 ma @ 5V. I have a couple of the adaptors already and have seen some nicer ones for less than $10, cheap
insurance against computer failure.
Edit: Checked that battery rating and it's a 360 mah battery, kinda at the low end of what is recommended for lr attys but should be ok.