I was wondering how hard would be to mod a regular radio transmitter with hall effect sticks, like this one:
Hardware wise, might get tricky but doable. Software/electronic wise that I am completely unsure...
Besides that they're probably prohibitively expensive and not all that much of an improvement over the regular sticks (assuming a quality transmitter - a cheapo won't be worth modifying anyway), it should be easy and it doesn't take any modding, just a stick swap. You wouldn't need any software changes at all and on the hardware side, the right model (0..5V out) is likely a drop-in replacement (i.e. 3 wires per axis tops), although you'll have to check the particular transmitter.
But unless you have a very expensive transmitter, I don't think it makes sense, as the sticks are probably more expensive than most transmitters.