Well good luck then, sounds like a very neat project. I'm almost tempted to make one myself.

I'd be very careful charging ipods and stuff. There is a limit to how fast they can be charged before blowing up. A typical USB port puts out .5 amps give or take. Those devices were designed around that spec, so charging them at higher amps can be dangerous. When lithium ion batteries overheat they explode, and charging it causes it to heat up and charging it very quickly won't give it time to cool, causing it to overheat.

RC stuff should be fine, but tred lightly, you could reduce the operating life.

It occurred to me that the reason the guy in the video was using two resistors in parallel was to dissipate the heat. So, if needed, you could run four 10 ohm 30 watt resistors in parallel and still get 2 1/2 ohms, and a better heat sink. Another reason may have been that those were the only resistors he had laying around.