People will either have an Arai or Shoei shaped head, buy whichever one fits you the best. That's if you are choosing top line stuff, however if another make fits you better buy that, in the past I have had Agv, Ogk, Laser.
A poor fitting expensive helmet will do more damage than a good fitting mid\budget choice.
Alarms are a waste of money, insurance won't even give you a discount if fitted, as people just ignore them.
On a side note rac\aa\greenflag the most calls out after punctures are bikes with failed datatool alarms.
A tracker will work, but are expensive and cost per month for the monitoring service.
You might want to ask Michael Schumacher how well helmet mounted cams work......
One mounted somewhere on the trike will be fine, gopro being the go to choice.
Tomtom have an action cam that is far better than the low cost would suggest.
Muvi are another make I have used, good results from that.
Great quad pic's.