Thanks for the replies gentlemen, that's what I value so much in this forum, the immediate feedback, what a great place!
The Sensorcom-inductive earpiece-neckloop-set is pretty lowpriced (around 190 euro's), it's just that I never heard of the brand. For that kind of money it's worth the try, and I assume that the soundquality will not be much worse than the Comtek/Phonak route.. I've used the phonak-invisity for the same reasons, and aside from being a very expensive option, I have had some interference problems with them, and that's no fun at all for the actors.. I agree that the off the shelf earpieces can poke out one's ear a bit so close-up shots are a concern, but the director and DP are more than willing to work around that, so it doesn't have to be a problem. The earpiece will probably only be used a few times during the whole shoot (long feature), and to me it's the only way to playback music on set where only the actor has to hear the music... I agree that for tv-series where such devices are used frequently on the same actors, a custom-molded earpiece is a better solution. I have two latex custom-mold plugs to protect my hearing at concerts, and they are nearly invisible..