If I could throw in my 2 cents worth on this...
I thought about that when building my first set of armor. I also thought about someone's idea where they used a pouch that hung around their neck to hold a wallet, phone, etc. The truth is that I just keep these items in my bin. I have been on countless troops, and never, ever felt uncomfortable about doing this. 99% of the time, the bins are kept in a secure area, and I don't even lock it. We tend to be a very honest, respectful bunch of folks, and I trust my fellow 501st brothers and sisters implicitly.
Once in a great while bins are stored in an area where the public may have access (this is very rare), so I just lock it and keep the key on an elastic band around my wrist under my glove.
If you want to keep your phone on you at all times (as some do) it should be turned off during a troop, and if it is in your backplate you couldn't get to it anyway. Just food for thought....