1. If your wingman is saying "Music On", it means that he has turned on his active jammers.
2. Most of the better sims will give some indication of this. In Falcon 4 SP3, IIRC there will be X's over the contacts using jamming. In LOMAC, it depends on your selected aircraft. Jane's F-18 has some indication as well, but I can't remember what.
These are the only recent sims on the market that I can think of right now. Hope this helps.
Deacon