An accelerometer may be made using the properties of light and the theory of relativity. If a Infra Red laser source is placed at one end of an evacuated tube and a similar one at the other, then if the beams are pointed towards each other then the two beams will meet.
If a diode is placed in the middle of the tube, then if the tube is at rest or in a condition of uniform motion, then there will be no signal from the diode.
If the tube accelerates along its axis then the diode will have two beams at different frequencies meeting and due to the non-linear effect of the diode then there will be a beat frequency generated.
I have derived the approximate formulae:
Where D is the length of the tube, c the velocity of light and a the acceleration. As an example if the tube is 10 meters long, c is 3*10^8 meters per second and a is 10 meters/sec/sec, then the beat frequency (Delta F)*2 will be 6.66 x 10E-8.
This indicates that there will be difficulty measuring the vlf pulses. It would be a question of measuring the time between them, ie 173.61 days.
Thus this crazy idea is not practical.