Mac Timekeeping System

My uncle has a small cleaning business and he uses a telephone timekeeping system so he can easily keep track of employees clocking and out. He would like to be able to replace the one he's got as it's been having issues recently and it's 15 years old. He would like a Mac-based one as his current timekeeping system is running on a Windows based IBM clone. His current timekeeping system's hardware consists of a PCI card which has phone line ports on it. He would like to be able to have two phone lines for it to prevent busy signals when a lot of employees are clocking in and out. Either USB, Firewire or maybe Thunderbolt interfaces/connectors are preferable to PCI/PCIE because it they don’t require a $2500-3000 Mac Pro, and instead can be run a $600 Mac Mini. Also, the ability to receive no-show alerts by email is critical, that way my uncle can arrange for that job to be taken care of by someone else if the person who normally does that job doesn't show up.

Also, it has to function over the phone lines rather than over the internet because very few of my uncle's employees have smartphones, and some of them don't even have basic phones. So, they have to be able to use a basic phone or a landline at the job site to clock in and out. By the way, they are to be identified by their employee PIN number, not their phone number. This way they can clock in and out on any phone.