If its in addition to a full kit, I would personally concentrate on lifesaving items in the small kit and leave things that you wont need instantly in your full kit. The things I would personally like in an "Instant Access" kit are:

Gloves
Resus face shield
Extra Large serile dressing
Triangular bandage
Asprin (for immediate treatment of AMI)

And make sure any other people you are with have any medications they may need in an emergency, (epinephrine autoinjector, salbutamol inhaler etc) and that you know how to administer them if necessary.

These are the things that will save lives, plasters and painkillers can always wait.

Chris