I been using Ride-On sealant in my tires for years:
https://www.ride-on.com/prod_mot.asp
So , was not sure how to answer the poll as I do not "carry" the stuff with me, it is already in the tire.
I do have some sticky string for plugging holes, which I have used successfully on my car tire, but usually I do not carry it with me on the bike, nor an air pump.
On long trips I might stash them on the bike, but so far I have used them to fix other riders flats..not any on my bike.
I think those that believe they should trash a brand new tire because it picked up a nail in a "plugable" part of the tire are just paranoid. Or rich.
These tires are not running 200 psi and most of us can feel the diffrence when the air pressure gets low...so even if a plug of sticky string were to blow out somehow, the rate of air loss would not be so sudden that the rider wouldn't know it and not be able to pull over safely and re-repair it.
As for the Ride-On...I am a supporter here. I personaly have not had a flat , so I can only go by other riders I know accounts, but the stuff seems to do a good job. A freind took his Wing in for new tires not long ago and the wrench showed him the inside of his old rear tire...there was two inches of a large nail sticking out of the center tread area. He never knew it was there.
Now some will say that is a bad thing, my thinking is if the tire never leaked and was rode to the point of replacement with the nail in there, then the Ride On did it's job.
You should of course visualy check your tires periodicly, along with checking the pressure, but I have not known or heard of anyone having a safety problem with a plugged tire..other than having to re-do a poorly installed plug.
KM