105 staff and 1 iPad to start with but would like to eventually get another one so regardless of which iPad is used it will allow to enter data or search data. So this sounds like server side right? Is this easy to do?
Time keeping. You have some SERIOUS legal requirements to consider.
Don't modify a DBMS in real time. What you are going to have to do is keep a LOG FILE the maintains a list of all the sign-in sign-out events and keeps some kind of PROOF that it was the employee who did it and also some kind of proof that the log file is not tampered with. You can use checksums to show non tempering and as for proof of the right person the web cam seems like an ideal solution.
If some one disputes their pay you are going to have to prove your case.
A SQL DBS is a dynamic thing. Even a table holding "events" with times is not a log file. Because at any time records of events can be inverted or removed.
I think you want the iPad to be a simple terminal that send events over an encrypted link to a sever machine. You could have any number of iPads.
Have the iPad(s) send the event (and wait for a reply) but also keep a log locally. If you use a DMBS at all that is all on the server side.
Be sure to keep a mirror of the data and logs in real time off site
It's hard to believe that you need to write this yourself. Sounds like re-inventing the wheel.