Alan,
There are 3 things that i can recommend:
1 - A really good FIRST AID kit. If you are like me it will be used often.
2 - An industrial fire extinguisher. No explanation. Get several judging by the size of the shop you want to build.
3 - If you decide not to put a phone, then you should at least get a decent intercom. Connect 1 in the shop and 1 in
the house. If you get injured (anything
that #1 won't handle) then you have a way
of reaching someone in the main house.
BTW, let us know when you start to build. We
will come down and give you a hand.