Access Control often is great for people entering a facility, but as the others mention, getting people to sign out is always a challenge. I worked in ITAR compliant buildings for several years and, naturally, we had security desks monitoring and checking the flow of people from the facility. For businesses that don't have this level of infrastructure, something like what you're describing is a good first step.
I think one of the key attributes of a system for tracking people at a facility is that you should make the presence of a non-employee very apparent. An example I've seen is a peg board that has essentially tokens hanging on hooks. Visitors get a token when they arrive (could be anything ... use a plastic fork if you want) and have to hang it back up when they leave.
This particular facility had the board painted so it was obvious when a token was missing. The goal of the system was not necessarily to have all tokens accounted for (people always were leaving with them still in their pocket), but to raise the awareness of WHY a token was missing. Is that person still in the building? Who are they? Etc, Etc.
The solutions that are most effective at physical access control involve a system and culture of awareness about visitor tracking. Making the tracking mechanism highly visible is something I think is important. Anyone who walked by that pegboard and saw a missing token had to decide to not say anything, and that encourages people to be responsible and take part.
That said, if you are looking for a good visitor management system that does things like printing adhesive badges, etc (and is ITAR compliant, btw), this one is super easy to set up: The iPad Receptionist
We looked at a bunch of these systems and this one had the most transparent pricing and best feature set. Took about 5 minutes to set up.
Hope that helps. Sorry for the long post.