Firstly, yes a cell phone. It's always in my pocket when I'm in my shop. For serious injuries it's good to have a professional available. In the shop I keep some tape, clean paper towels, band-aids and wet wipes in an old tobacco can. My shop is in my basement so I can access my home first aid kit easily. It's in a small backpack and I assembled it based on the old Army combat lifesaver bag. (I can't reasonably get everything in the newest version.) I've taken the 40-hour combat lifesaver course twice. Also a copy of FM 4-25.11 First Aid. You can get it from Amazon for $10. Or you can download it here:
https://archive.org/details/FM4-25.11
And I try to remember to inventory my first aid kit twice a year. This is a copy of the checklist that I use:
First Aid Kit As of:_____________________________
1 FM 4-25.11 (December 2002)
1 7.25" Surgical Scissors
1 Pocket knife with spatula
1 TK4 Tourniquet
1 Nasopharyngeal Airway size 28 Fr (9.3 mm/0.37")
1 Wash cloth
2 pair disposable gloves
1 Cravat dressing - Army (37" x 37" x 52") (NSN: 6510-00-201-1755)
5 Pressure Dressings - Army (NSN: 6510-00-159-4883)
4 Compress and bandage - Army (2" x 2") (NSN: 6510-00-200-3075)
12 Butterfly sutures
1 Roll gauze (4.5" x 3 yards)
1 Roll gauze (3" x 6 yards)
2 Gauze pad (8" x 4")
4 Gauze pad (2" x 2")
1 Roll surgical tape (2")
1 Roll surgical tape (1/2")
1 Iodine bottle (2 oz.) Expires 07-18
2 Cold packs
1 Ace type bandage (2" x 36")
1 Band-Aid (bundle)
1 Q-Tips (bundle)
1 Antibiotic Ointment (1 oz.)
10 Ammonia Inhalation Ampules
1 Field Splint, SAM, 36"x4.5" (NSN: 6515-01-225-4681)
1 Flashlight
_ _______________
_ _______________
_ _______________
_ _______________
Or, to quote Bill Murray, 'ARMY TRAINING, SIR".
(I got most of the Army dressings off ebay.)