tl;dr: A solid value for a reliable wireless mic solution. Perfect for most uses up to 35', and usually good even further away.
The Audio Technica Pro-88W lavaliere microphone system is a very good wireless lavaliere microphone system for a very low price (in comparison to most quality UHF systems). I've been able to use a wide variety of wireless gear, costing from tens to thousands of dollars, and for my money and my projects, I'm quite happy with the Pro-88W.
The Pro-88W is not built like a tank, and it's not as robust in terms of clarity and signal strength as a $500+ UHF-band wireless system, but I would rate it as the best VHF system, and arguably the best wireless mic system for under $300.
Here's a sample recording from my Nikon D7000:
(I apologize for the horrible lighting. I was moving the week I recorded this video, so I had no lights!)
The Pro-88W/R sounds just as good as any plug-in lavaliere within about 35' of the receiver. Once you go past that point, the quality of the sound and signal to noise ratio goes down depending on where you are. Some places, I get get a hundred or more feet away before I notice a bit of interference; other places get bad after about 45-50'.
The included microphone gives adequate sound, but you can plug any standard 1/8" lavaliere (like the ATR-3350) into the transmitter, to get slightly improved frequency response, and a longer cable to boot!
I've used the Pro-88W/R with an iPhone, my Nikon D7000 DSLR, and my Mac, and in all cases, the level was good, the sound was great, and I wouldn't hesitate to use this wireless lavaliere instead of a wired mic in almost any circumstance. The only downside to this mic (and any wireless mic) is that it requires fresh batteries.
The kit also includes a really cheap mono earphone, which works, but feels like something you'd get with a happy meal toy. I tossed mine back in the box, and haven't touched it since.
The Pro-88W/R feels pretty solid. The transmitter and receiver are each a little bigger than a box of playing cards, and are relatively thick compared to pricier bodypacks. However, they're built well out of a scratch and smudge-resistant plastic, and all the connections (especially the screw-on antenna) feel sturdy.
The receiver includes a hotshoe mount, so you can put it on top of a video or still camera, and a 1/4" adapter so you can mount it on a standard tripod screw. There's also a coiled cord to connect the receiver's output to your camera's input, an extra belt clip, and a long, rubber, detachable antenna.
This microphone works great with any audio equipment with either mic or line-input, including smartphones and cameras like the iPhone 5, iPhone 4/4s, Nikon D800, Nikon D7000, Canon 5D mark III, Canon 7D, etc., and many consumer and prosumer video cameras. See my article on using external microphones with the iPhone 5 for more info.
The included manual is well-written and has illustrations so you don't get lost.
The mic and receiver both require 9V batteries, and will use them relatively quickly (I'd say expect maybe 5-10 hours of good quality transmission, maximum). I always keep at least one spare set of batteries in the bag in which I carry this mic system.
This is a great wireless microphone system. I think this mic system is the best value in a wireless mic for under $200, and it includes everything you need, and all the right connections, for recording decent sound in situations where you need a lavaliere mic.
Buy the Audio Technica Pro-88W on Amazon for $120.