Spider Tracks or something similar is the way to go. ELTs are unreliable. Having seen how Spider Tracks works in real life when the ELT failed to work after a fatal accident convinced me. The owner knew the aircraft crashed within about 5 minutes of the accident happening and where. Didn't save any lives as they were all dead, but it did provide valuable information to where the crash site was.
If I was going to purchase an aircraft, this would be a must fit piece of equipment that I would fit. Aircraft can be monitored from a mobile phone through an APP.