You might be able to use a Digital IO card to handle signals from devices.
An optically isolated IO card could give you about 16 channels or more per card. Each device normally only needs one or two channels for the High or Low signalling.

This is how I worked the control for the Walt Disney World Epcot Globe video control system, although I used a combination of C++ and Visual Basic. FoxPro support dll calls and ActiveX controls so you would be able to handle it as well.

A company called NiDaq has the cards for sale. Look for Data Aquisition for researching the topic.

By the way, digital io works great for most electronic devices because all it expects are low and high signals. generally 0-5 volts.