Have one for several years before upgrading to the XRX unit. It was useful for getting your attention in a hurry and got me scanning outside the aircraft urgently ( and yes, I always scan outside before anyone complains !)
The MRX only gives you distance and relative altitude to the target and does not interface with any GPS unit.
The more costly XRX also displays relative bearing to the targets ( up to 3) and can interface via Bluetooth or serial cable to several handheld type GPS units.