When a business gets to the size of needing something bigger and better than a book that staff just sign in / out of, the next step is often to make it part of the responsibility of the receptionist to manage the process but continue with the book.
Otherwise it is a simple time recording swipe system, with a card for each employee and a pool of numbered cards for visitors. But there's a overhead cost of running such a system.
Logging staff who are in the building but on lunch is not a H&S issue - it falls under the time recording / payroll bucket. One either has to have managers managing their people (and that includes time-keeping and attendance) or it can become part of payroll and is run as an administrative process. Given the type of company you say you are, I'd stick to logging people in/out of the building purely for the H&S reasons.