A small zip-tie holds the zipper(s) closed, and makes a tamper resistant seal, there is a dated tag attached by the zip-ties. Each kit has a dated contents checklist in it, when the kit is opened stuff is used, and is replaced ASAP, and the kit resealed.
I've never had a problem getting past a zip-tie, I can tell at a glance if someone has been in a kit. I often deal with sharp knives, sharp tools, power saws and fire.
My Garage is 150' from my house, the bathrooms are on different floors. Experience has taught me a kit in the house does not help with cuts in the garage, or when in the vehicle. I take pain meds as little as possible, so meds in a kit are not used often at all. I check each kit, and my emergency bags on New Year's day (along with changing my smoke/carbon monoxide detector batteries), and each time change day.
Overkill for many, but works for me!
I also have a resupply cabinet in my master bath, which has boxes of ready use bandages and meds.