Hi Trish and welcome to the forum. I assume you are in the UK but I'd suggest you add a rough location to your profile so you will get more targeted replies. All GLCs come fitted with a tracker by virtue of the car having its own SIM card installed. You always know where your car is in a "find my phone" kind of way. The Mercedes Me app for your phone/tablet will show you exactly where your car is and I believe you can also set a ring-fencing feature which automatically notifies you if the car strays outside a predesignated area. These features are free of charge until your 3-year warranty expires then it becomes a subscription service if you want the facility to continue.
I'm not sure if a wireless dashcam exists in terms of wirelessly powering the device but many allow the wireless transfer of captured footage to either the Cloud or other storage medium. Halfrauds are running a 20% off promotion on certain dashcams at the moment so one of those may be suitable for your needs. They will also do the initial installation for you from £30 depending on the complexity. This front + rear dashcam package is on offer at £159 excluding fitting and seems to have been very well received by customers looking to protect themselves from the crash-for-cash merchants:
If you want a much more upmarket device look at the Blackvue range where the flagship model offers a front/rear combo with capture in 4K resolution. This would probably cost just shy of £1000 professionally installed:
In Australia, no SIM card and no Mercedes Me app either. Disappointed.
Would need to fit an aftermarket GPS tracker, with a sim data plan, my best guess here.
Re Dashcams, yes, Blackvue and Thinkware both good brands, with front and rear cams and wireless connect, no screens, adjust from phone screen, some with Cloud storage as well as micro SD card on board storage, both have ones that are low profile, minimalistic.