I got a vacation vault, if you do a search it will pop up. Basically it is a plastic box with a locking strap. It's hard to explain, if you go to their website you'll see. It is relatively small, unfortunately it will not hold my 10 inch tablet

It will hold a couple of cell phones, camera, glasses, wallet etc. You put them in the vault, then you wrap the strap around something before you lock it. I usually leave mine in my bag, with the strap coming out of the top of the bag, then wind the strap through the openings in my chair. Then you lock it, it is now locked and fastened to your chair. Then I throw my towel over that. This way nobody even knows it's there. It makes it so that nobody can just slip their hand in your bag and take your phone, camera, or whatever. It is plastic, so if somebody wanted to break it, they could, but I really don't think thieves would want to draw that much attention to themselves. Somebody would notice someone trying to bus into your plastic case with a rock. They can't easily cut the strap because it is cable on the inside. We have annual passes to our local waterpark, so we use it there all summer too. I find it really convenient, and I never have to get a locker. You even get to set your own 3 number combo.
I also bought one of the small plastic cases you wear around your neck. I got mine at Typhoon Lagoon. There is a small one that is maybe half an inch deep, and a larger on that is like an inch or so. If you have a small phone it might fit in the larger one. I have the smaller one and just keep my credit card, room key/charge, and a little cash. That way if we decide we're hungry or thirsty we don't have to go find our chairs, which would certainly be on the other side of the park, to get to our money. We bring our own colored beach towels, makes it so much easier to find your chairs.
Have fun!!!!!