I have considered the forearm, part of why I was planning on my hand was fear of hitting a vein/tendon near my wrist 
I am aware, of course, that these are everywhere in the distal arm.
My concern is e.g. if I were to implant superficial to the midpoint of the base of the extensor digitorum tendons and the base of the wrist:
I would be concerned about the amount of movement the implant would be exposed to from the tendons. Likewise for the same location in the anterior part forearm, i.e. superficial to the flexor digitorum superficialis/flexor carpi radialis:
I am thinking P1, P3, and P4 would experience less movement than the prior two locations, but I may be way off base in that opinion and would love to learn why I’m wrong.
I’m now thinking that between the brachioradialis and the flexor carpi radialis:
May be a good spot as far as isolation from tendons and being distal to the arm (which I think I would prefer more than the proximal arm as far as convenience/ease of use goes). Would the proximity to/movement of bones involved in pronation/supination of the wrist make this a bad spot? Would appreciate any input on that and any of the things I’ve said prior in this post. Thank you!
TL;DR: thoughts on implanting below the wrist (anterior and posterior under consideration) and between the brachioradialis and flexor carpi radialis compared to P1-P4?