it depends on wireless restrictions in your area ... i would stay out of uhf if at all possible because it will most likely compete with any wireless mic's for spectrum.
so that leaves you a few options
1. 900 mhz not too crowded and similar propagation to uhf 470-698. must be digital and must be spread spectrum clear com has one of the only solutions in this range we have and are fairly happy with it.
2. 2.4 wifi ... not bad a few of the major brands telex and clear com have solutions here but its is going to get increasingly crowded at major events if it already isn't i read somewhere that major cell providers are actually paying stadiums to install massive wifi networks to help offload their networks some at large events.
3. other vhf/1.9mhz riedel has a solution that works on 1.9 seems promising idk price range. and there is a new entry from makers of the popular helical antenna PWS has had some employees spin off a new company good read here:
http://www.tvtechnology.com/regulatory/ ... ons/218898stick to wired if at all possible !! otherwise go i'd suggest go licensed 2 way radios for any essentially wireless personnel ... fyi this is all based off of rules in the US.