Covered in other threads - this is one:
For yourself it is always prudent to keep a medical summary card on your person. Include:
Emergency Contact Numbers and Names
Any known medical conditions
Any known allergies
If traveling with a group make multiples and trade with others so the info can be made readily available to emergency personnel. It is a good idea to adjust your kits based on what you will be doing and if possible coordinate some items with others in your group. I do sport-tour rides (nothing off-road yet) and have to fit everything into my tank bag and suit pockets (no saddle bags).
It doesn't matter what supplies you pack for emergencies if you don't know how (when) to use them. After I took the ASM course, I put together the following emergency kit for my bike (with the full knowlege that if I am doing anything that requires touching another person - beyond hand holding - that person is already sooo beyond screwed
6 individually wrapped sanitary napkins - ultra thin, no wings, no deoderant
6 individually wrapped tampons - no applicators, no deoderant
1 roll of gauze
1 mylar emergency "blanket"
1 pair of shears
2 pair of medical gloves
1 disposable cpr mouth sheild
1 4 oz bottle of saline
Cell Phone - serves multiple purposes!!
That covers the medical portion of my kit. I have feminine supplies instead of gauze/cotton pads because the are very absorbant and take up very little space. Also (for some of us) there is more than one kind of "emergency"
I keep the gloves, mouth sheild, notebook, pencil and cell phone in my jacket pockets and pack the rest into the tank bag as tightly as possible. I hope like hell I never need to use any of it. This reminds me, time to take a refresher so if I do need it, I can be as prepared as possible for a non-medically trained bystander.