Road Tandem:
Small seat pack under my saddle (don't you love the mixed lexicon) contains a rolled-up / foldable tire & small first aid kit with wipes and adhesive strips.
Small seat pack under Debbie's saddle contains a tire lever, one or two tubes, a Crank Bros. Micro 17 mini-tool, a patch kit with a couple SuperLink III's, three links of spare chain, a spare valve extender w/o-rings (we run deep section rims), a vial with both Tylenol and Advil, and one spare Frog cleat**.
Money, keys, ID, and food go in the jersey pockets.
Blackburn FP-1L is attached to the underside of the internal tube on Debbie's 1/2 of the tandem.
Off Road Tandem:
Med. size seat pack under my saddle contains 2 tire levers, one tube, a Crank Bros. Micro 17 mini-tool, a Park compact chain tool, a patch kit with a couple SuperLink III's, three links of spare chain, and if I remember to move them over from the road tandems the vial of Tylenol & Advil, the small first aid kit, and spare Frog cleat.
A Blackburn mini-pump resides in my Camelbak along with keys, ID, and food.
**While incredibly simple and reliable, if you let your Frog cleats go too long the small little elastomer piece with the metal ramp that keeps your shoe attached to the Frog pedal WILL quietly fall off and there's nothing you can do to fix it in the field aside from duck-taping your shoe to the pedal for the ride home, ala 'Breaking Away' (been there, done that as recently as our 3 Gap ride before watching the Tour de Georgia come through Dahlonega. As Tim Allen would say, if you can't fix it, duck-it!