Okay here's a bit of an overview of the various systems that I stock.
To be wireless you need a transmitter and a receiver. In the Minelab gpz & ctx the transmitter is built into the unit. In the Makro Racer 2 & Gold Racer you have a separate transmitter/dongle that slides into the side of the control box. This is supplied with the Makro Wireless headphones. Note: these only work on the Racer 2 and Gold Racer. (Red Racer uses Bluetooth.)
The advantage of these "built-in" transmitter systems is that they don't need to be charged, they just run off the detectors main power supply. The disadvantage is that you can only transmit to the supplied wireless receiver unit, i.e WM10 (ctx), WM12 (gpz) or Marko headphones. The other disadvantage is that you cannot use this system on another detector.
A universal wireless system like the Deteknix WireFree system and now the Minelab Pro Sonic is that the transmitter plugs into a 1/4" headphone socket, so can be used on any machine.
Deteknix have a few different systems. All come with a transmitter with 1/4" plug or Garrett AT Connector (slightly more expensive).
WireFree Lite - these are the light weight, small, on ear headphone. Excellent for hot conditions and for coin detecting.
WireFree Pro - these are the full size headphones, better sound quality and much better noise isolation than the Lites.
WireFree WR - this is the wireless kit, transmitter and receiver units (no headphones). This is great for people who already have their preferred set of headphones or booster/speaker combos but just don't wish to be connected to their detector. Also great if you wish to use earbud phones which generally have short flimsy cables.
All the Deteknix wirefree products use 2.4 Ghz wireless technology, not Bluetooth. Bluetooth has a bad delay, supposedly much better in the low latency versions, but the other thing I dislike about Bluetooth is that it transfers compressed/mp3 style audio.
All the WireFree products are interchangeable. I.e. if you bought the Lite headphones for a Garrett AT, you could buy a 1/4" Transmitter only and use your existing Lite headphones on another detector.
Hope that helps explain it.