The "Contraption" I've been messing with for the past four years has what some would probably call an ionic antenna. Point it at the target and it beeps. Not always though. Don't know anything about this one but I assume the ionic part is similar, but is a different configuration.
I have untold number of hours on the pivoting antenna type locators. They work if you can learn to use them, but most people never get the quiet mind. They all think they do but they don't. That's why i say it is essential. I've posted some GSR info. The first thing you will find out is your mind is jumping all over the place--like a wild horse. Takes twenty minutes to get calmed down, maybe faster once you have much practice.
A cheap one called Grove GSR hooks up to an Arduino (or Raspberry Pi). Probably under $25 with a counterfeit Arduino. Easy to hook up to your computer (but takes some time to get Arduino on your computer, gotta follow the directions) and watch the graph on the monitor (along with some yoga breathing). This is all you need to help learn to reach the Zen-like state.
http://wiki.seeedstudio.com/Grove-GSR_Sensor/
https://www.ebay.com/itm/UNO-R3-Boa...054374?hash=item1c5d384a26:g:prwAAOSwFb5aN1fb
The Arduino link is just an example. Look around for best deal. But you will need the USB cable. I didn't use the "Base Shield" Grove sells, just hook up three wires but you can spend a few more dollars if you want it to look nice and a bit easier to hook up to the Arduino. You don't need a power supply for anything. The Arduino plugs into a USB port on your computer and does not need a power supply.
Yoga breath you just slow inhale through your nose at count to five, hold count to two, exhale count to five. Follow your breath in and out. Don't think of anything else. If you get distracted, just get back centered and continue. Do that for twenty to thirty minutes twice a day. Don't expect any results for eight weeks. Once your mind is quiet you can be more aware of the subtle energies. Again, this is for the pivoting antenna type locators. The Contraption does not use a pivoting antenna--just point it and it beeps.
Just repeat I would not spend that kind of money on any locator. If some day I get the Contraption to market it should be under $1000 if I can get it mass produced, maybe even less.