The I/OLinc only has a dry input. The 5V has nothing to do with the input. I can trigger the sensor on mine by just shorting the GND and Sense and ISY reports it either On or Off. The 5V purpose appears to be a convenient source for running 5V through the relay circuits for controlling power to devices, if it requires 5V. My application requires 12V so I use an external power supply plugged into the I/OLinc.
I am told the EZIO 2x4 should work. I have one on order and will followup when I get.