My professional wireless background is far more involved in audio headsets than metal detectors so I'll strive to be brief and specific on the topics in this thread. (brief is difficult for me)
Bluetooth (a technology brand) is indeed a more widely popular standard than Kleer (a company name which uses a proprietary technology). Kleer based products almost always come in a pair a dongle (plugs into audio jack or maybe USB) and a headset. Kleer main claims to fame are low latency and lossless audio (in laymen's terms this means very clear audio). So, to support vanerspaul's assertion, you are not likely to go wrong with Kleer based audio jack dongle and headset.
Bluetooth headsets tend to be sold standalone to work with a phone, computer, tablet, which has an embedded bluetooth capability. If you find a Bluetooth audio jack dongle and headset combination, look for "low latency A2DP". Otherwise you may end up with a latency problem as Steve notes above.
(OK, one nerdy thing - for lip synch audio, matching video human speaking to audio, the rule of thumb is less than ~ 40mSec latency. So in our application, matching MD swing (eyeball) to sound, look for less than 40 mSec latency on the specs of your headset audio dongle combo.)
To summarize for those not wanting to be wireless audio pros, you are less likely to make a mistake with Kleer based audio dongle and headset products.
The GPZ 7000 is based on a 2.4 GHz proprietary technology of Texas Instruments (per FCC submissions). Bluetooth and Kleer also use the 2.4 GHz band. 2.4 GHz is not in and of itself magic. There is crap and great audio stuff using the 2.4 GHz frequency band. Minelab's choice of the TI technology means they are going to keep their wireless audio link a closed system so you can't go buy a wireless headset to mate with your GPZ 7000 directly. You'll buy a corded audio headset to plug into the GPZ 7000 WM 12 just like on the CTX 3030 WM10 module.