I live in Greenville, NC and I'm a contract engineer but currently between jobs and not expecting to get busy for a few weeks. I can drive over to Charlotte once or twice a week to knock this out. Normally I work on automation for industrial plants such as automated tire manufacturing machines (most recent), safety systems for kilns, large robots (google "dragline"). My normal rates are a bit higher but I'm between jobs and I normally change my pricing depending on the job, so don't let the "big gun" background scare you.
My thought right now is that you need an electromagnetic door lock...probably nothing too complicated since you already know what you are doing with the rest of the setup. Best option would be something off the shelf, probably 24 V powered, if you don't already have a lock that you like, so that you can keep a spare handy that can easily be replaced...nothing like having to lose business on account of not having parts on hand. We can scale it up from there depending on what kind of interfacing you want on the other end.
If you are interested or have further questions, contact me on my cell phone at (248)289-3106 or E-mail through the web site.