in ear monitors?

simple terms ---- earphones

Yeah but not the $5 variety you get with your walkmans. Studio quality In ear monitors run upwards of $300. And they sound better than most phones that are dj "standards".

Also allot of performers are using them on stage these days as well.

so does that mean you dont need fold back speakers if you have an in ear monitor?

Yes and No, usually if the use the in ear monitors they are performing smaller shows. Like when you see performers on the MTV movie awards. They won't be that benefial playing in front of 20,000+ screaming fans.

actually have spoken with many pro's that are with big travelling bands and a lot of them are going to these setups. 300.00 range is actually cheap for this...
carvin makes a cheap version of this..
PM1000 - Professional Ear Monitor System and they sell theres for 299.99 with one reciever and 1 headphone.. additional headset units are PM1001 - Professional Ear Monitor - Extra Receiver and are 129.99 each... but include the earphone and receiver...
any unit cheaper is not worth owning...

as with any wireless device... anytime you have multiple wireless devices you can get what is call "crosstalk" most people laugh with the "breaker, breaker, this is rubber duck" thing but, this can happen.. so, if you plan to order from anyone check with you locals and make sure that you are not going to be in a zone that is frequenced by others... also, i remember receiver cell calls on my walkie-talkie a few years ago...

we were using a duplex system at a church production in the middle of it we hear" I cxan't see the runway I'll have to circle around again it's all fogged up" the worst part is we were 15 miles from the closest airport.