What are those glass things you see on tv that water plants when the air bubble rise to the top?

Question

saw the add on tv...

Answer 1

I just bought these and do not recommend them!  When you put them into the plant pot, it gets blocked with dirt and no water comes out.  I've tried everything to get this not to happen to no avail.  I've had these globes for 2 weeks and I've tried more times than I can count to correct the problem, but it's just not working.  My ivy plant got so dried out at the top, I'm not sure if it's going to survive even.  The concept is a good idea, but just not working.  Don't waste your money.

Deanna