I assisted with the timing of an event where we needed communication between 4 moblile headsets between the finish line, the timing shack and finish corral. The distances weren't very great (about 250 - 300m), but the people had to be mobile and it would have been difficult to string wire to operatate the Alge headsets.

I connected two standard Panasonic wireless DECT 6.0 cordless telephones (4 hansets in total). Each handset had a small headset attached.

This worked very well and allowed people to walk around and communicate. The full-duplex communication was crystal clear. The phone batteries lasted at least 8 hours at our event (and are advertised as having a talk-time of 17 hours.)

Anyway, if anyone is needing some relatively cheap, short-range, wireless headsets, then an off-the-shelf cordless phone system might work.

My sister could use this. She's planning to put up an event coordinator sort of a business. Thanks.