There are two types of radios people use when hunting: VHF and UHF.
VHF Radios, also called marine radios, are intended to be used when boating out on the water for emergencies, ship-to-ship communications, weather alerts, etc. The handheld units go up to 5 Watts in power, which in the right terrain will easily get you 5+ miles of range. If connected to a external antenna in a vehicle, range increases up to 15+ miles if the terrain is relatively flat. Companies are starting to offer more accessories such as ear pieces and headsets for VHF Radios, but they still lack behind UHF Radios. A license is not required for their use, but I don't believe it is legal to use marine radios on land for any purpose other than weather alerts. That said, alot of people use them for hunting! If you're not near an area with alot of water and boat usage, interference with other non-hunting users should be minimal. Midland makes a good VHF Radio.
UHF Radios come in two flavors. The Family Radio Service (FRS) Band Radios do not require an FCC license, but are limited to a 2 mile range due to their low power of 1/2 Watt or so. The last time I checked, there were limited accessories available for these 14-channel radios, but that may have changed lately.
The second type of UHF Radios run in the General Mobile radio Service (GMRS) Frequency Band and go up to 5 Watts in the handheld radios. Distance is similar to the VHF Radios with the same power, but there are tons of accessories. An FCC license is required for legal use, but most people ignore that fact. GMRS Frequencies are also used by many businesses, so interference is often encountered with business such as small trucking companies and large farming operations with repeaters, etc. Motorola makes a good UHF GMRS Radio called the talkabout which are sold by Cabela's.
We've been using UHF GMRS Radios for coyote hunting for 10+ years in Illinois and Wisconsin. It is illegal to use the radios to direct people to game, especially if vehicles are involved, but are legal to use during the hunt to keep track other hunters, coordination, etc. There's a fine line on the issue of using the radios to direct people to game, but most game wardens don't bother people when the radios are used to hunt game such as coyotes. We have never had any game wardens question our hunting with the radios.
Is it ethical to use radios to hunt coyotes? I believe so. Without the radios, hunters on foot have almost no chance of getting coyotes. The coordination that the radios allow is the key. I would argue that using the radios is just as ethical as using an electronic game caller (which I use) or electronic tracking collars on dogs, etc. I guess it just depends on your point of view!