I'm using a redneck jerry-rigged IEM setup, that fits nicely in a small backpack:
A Behringer Xenyx 802 mini mixer, receiving 3 feeds:
- my monitor mix from FOH
- an SM57 placed sidestage, facing the audience
- a post-EQ line out from my Genz-Benz Streamliner 900
I back-feed the monitor mix up an idle channel on the snake, using a pair of cheap Hosa XLR gender-changers. The mic at the edge of the stage picks up a bit of the FOH mix, and audience reactions.
The reason I use the mixer, is that it gives me 3-band EQ and pan controls for each monitor feed. If something happens to mess up my main monitor mix part-way through the set, I can dial in more or less of the room sound to compensate, take the bass out of a heavy-handed keyboard player, etc.
I like having control over my in-ear mix, having stereo separation for the 3 feeds, and not having to try and get the soundman's attention when things go wrong.
Also, the headphone amp in the Behringer, combined with a hardwired, balanced monitor feed, sounds a lot better than what I was getting from a Sennheiser 300-series wireless rig. When I was using the wireless, I was constantly trying out different headphones. Now that I have the mixer, I'm perfectly happy with an $80 pair of Klipsch iPhone ear canal buds.
If I regularly worked with pro sound people, none of this stuff would be necessary. For the small charity gigs and church dates that make up about 50% of what I do, it's a real Godsend.