Yes. A Pantone Huey can be used to calibrate multiple computer/monitor combinations. You connect it during the measurement process, create a display profile for that specific setup, and then disconnect it once calibration is finished.

After that, each calibrated computer can be used normally at the same time without the Huey attached, as long as each system is using its saved monitor profile.

The main reason to leave the Huey connected is if you want its ambient light adjustment feature. That feature can only work on the computer the device is currently attached to, because it updates the display based on current room lighting. Without that, the saved calibration profile still works fine on its own.

In short: one Huey can profile multiple systems, it does not need to stay plugged in for normal use, and simultaneous use is fine. Regular recalibration is still a good idea.