We have a myhummy, we love it. It's not a miracle sleep solution in our case but does help settle our little boy during the night and during naps. It's great for when he's napping when we are on the move as it stops random sounds waking him and even at home it helps with that. And it's fab it kicks back in at night. He still doesn't sleep through at 8 months but he does stir sometimes and it helps him go back to sleep. Other times he just wants milk and nothing is going to stop him. Expensive but worth it in my opinion. Also worth trying eBay to see if anyone is selling one second hand, I picked mine up as new because they felt it didn't work for their baby and paid half the price.
Never used the owl but I believe that it only works for 3 hours at a time. Myhummy works for 12hours so lasts all night.