You couldn't be more right. A thief is a thief. The best thing to do IMO is prove they're stealing and fire them. There are plenty of honest people out there looking for work.I dont have a hardware recommendation for you, but I strongly believe that since you already have employees stealing from you (clocking in without being there is theft), no matter what system you put in they will figure out ways around it. I would simply notify everyone of the policy reminding them that any theft is a fireable offense. Put in a video camera. Then fire them. Also note that if they are fired for theft (as opposed to laid off) you dont pay toward unemployment. Wouldnt hurt to remind them of that too.
I have a customer who uses this system to clock in there employee’s http://www.timeclockeshop.com/acroprint-pendulum-hand-punch-1000-biometric-time-clock-system.aspx
They also have a HD camera system in place that can track everyone on the property so they can see what’s going on all the time.
We use a GPS tracking system in the company vehicles to track the movement and location of employees. It’s simple to install, installs into OBD port under the dash. It's an unbelievable system.