It'll slowly charge your devices, but only so long as you are hiking pole-wards.
I agree with Madires: It's a dinky little panel in sub-optimal placement. If you are doing serious days-long treks, this is completely inadequate, and if you are not then you really have no need for solar, just a few USB chargers that will cost and weigh less. You'd be better off getting a little fold-out panel you can lay out in the sun while you are stopped for lunch.