It sounded interesting, but I was thinking it would have been through quantum entanglement. Then I thought about the measurement paradox and realized I am not a quantum physicist.
Accelerometer navigation would be next to worthless without major computational power, and the device is hardly portable, so this seems to be a solution that is as complicated and fallible as the GPS system it is intended to replace.
What you said.
The whole point of the device is to be portable.
It just is not as portable as we would like it for most applications, yet.
The first GPS units were much bigger, and took more power than the current ones.
Inertial navigation is routine, and was “how it was done” on airlines before GPS, with various radio aides to navigation such as LORAN, OMEGA and DME. GPS has supplanted other forms of radio navigation. Modern navigation integrates GPS and inertial, but achieves satisfactory results with inertial only.