Do you have any upcycled uses for gel ice packs that you actually find useful?

I have several gel ice packs to throw out and would rather make use of them if possible. Some leak and others have been collected for various uses (chronic health related). Is the gel the same stuff used for plant seed starters or anything like that?

Sure, I could search the web and find lots of people selling ads with their impractical MacGyver anecdotes galore, but that says nothing about what is practical and worth actually doing versus conventional alternatives.