I have used a
power monkey explorer kit for about a year and it is very good (bought it on a whim from duty-free...you know how it is when you have your holiday head on..
.
The power monkey explorer rechargable battery is 2200mh capacity and outputs 4.5 / 5.5v @ upto 700mah, it seems to charge my Orbit2 at about the same speed as the Orbits official mains charger.
The power monkey solar charger outputs 5v @ upto 200mah, but will charge the Orbit2 or recharge the power monkey explorer rechargable battery in modest sunlight (wont do both at the sametime tho - even in V strong sunlight).
The power monkey explorer kit is very impressive all round.