Ive just read the article in the latest plumbers journal about these things and I really think they are a waste of time. I often get owners buying these things and expecting me to install them even though I never quoted to do so.
If a shower mixer is installed properly it wont leak. If it does leak so what? Any piece of pipe or fitting can leak! What are we going to do install all pipes in special waterproof ducts in case they leak and cause some water damage?

Get real!

Linkback: https://www.plumbers.nz/plumbing/1/aquatight-wall-caddys-what-a-waste-of-time/505/