I was looking into that too. Looks like mrmr only supports a very basic set of messages and is not configurable. Likewise, SL supports a very specific set of messages, so they are not compatible.
Two solutions, the first, as you mentioned is to make intermediate software that translates between the two interfaces. The second is for me to make a better, more general iPhone OSC app than those that currently exist. Actually, the third is to make an SL specific iPhone controller app, but I'd rather do the second!

FWIW, I am currently working on a multi-touch synth/sampler/looper iPhone app, I'll put you on the beta testing list when I get that far....