Hey everyone,

I've got a bit of a tricky problem that is outside of my scope of expertise and I'm wanting to pick your brains to see if any of you have come with a decent solution to something similar.

I'm trying to figure out a solution for a getting real-time understanding of how many people (staff and contractors) are located on each site and where they are located ie. floor. Essentially we have a number of sites that we would like to be able to identify who is inside a company building and where in the building they are.
This is the precursor to enabling Activity Based Working, the problem is that we don’t know who is where, when or for how long; we can't estimate our requirements without a solid starting set of metrics 
A bonus of this solution is that it will also dramatically increases physical security data in the event of something bad happening.

We can't use ‘log in’ from AD data as we do not and will not enforce forced daily log offs or restarts. We also have a number of people (a variable number) that VPN into the network. This is the same reason something like proxy log data won't work.

We can't use the current physical swipe card data as people will often tailgate each other through doors. We also do not force swipe outs, so the data is one sided. It's very unlikely that we would be able to enforce or maintain the level of staff discipline that a system like this would require in any case.

I’ve seen the physical under the desk mounted units and whilst they would work, they are outside what I’m wanting to pay if possible.
My thoughts were around using some form of passive RFID to monitor entrances and exits but so far I've been pretty disappointed at the options.

Do you have any bright ideas on how to solve something like this?

Thanks.