Please stop bumping your topics less than 24 hours after the last post it's getting really annoying.
Personally I've never heard of the term OMT, but from the sound of it, you are talking about a mean of payment like Paypal is, aren't you ?
If so your question n°2 is irrelevant (since it is a mean of payment, not an income source).
Otherwise, I don't know what you are talking about and you should likely do a google search, as usual with your questions, before asking them here.
Or at least give more informations like where you've heard from it and why you feel like asking this on Scirra's forum is a good idea in your opinion.