Even a little light could make it visible at night. A photonII or some other lightweight LED light would not weigh down the kite much.

The kite would be dependant on wind being not too hard and not too soft for teh individual kite and string. the slingshot would be dependant on at least one good hand, it could be lashed and used one handed.

Even with the slingshot, hurling a small light up every few minutes might attract some night attention, getting the light above the brush. Or throwing a line in a tree and hauling a light up above surrounding clutter?