The Smart tire inflation kit is identical to one by Continental Tire (same as created the tires) and is sold by TireRack.com for about $30-40 as a refill. You can also get a plug kit or a Nealy's Tire Repair Kit online (
Nealey Tire Repair Kit) and fix it yourself on the side of the road, provided you have the strength and energy - not a lot, but more than just changing the tire.
I don't think tire warranties are appropriately named -- that implies a full-service replacement of a defective part, when in fact this is a patch/fix for an event beyond the tire maker's control. Everyone gets a screw in their tire at some point, and roadside assistance such as AAA will only help you with the labor, really -- muscle the tire onto the car, drive or tow you wherever so someone else can fix it at your cost. That's not a warranty... it's a service contract.