I was thinking the same thing a few years ago. I paid $30 for 6 AquaGlobes to water my 6 seedlings while I was gone for 8 days.
I thought I better try them out first so I set up one globe on a seedling needing water. Didn't need water long! The globe emptied
in 45 seconds. Shit, I coulda done that with a free water pitcher instead of $5 globes.
Thought -- I was using real loose soil at the time. Maybe if you tamp down your soil first the globes may not empty immediately
like mine did. Anyway, be sure to test it before you leave.
Good luck, BigSteve.