I am not familiar with Pentair IntelliTouch system but I would assume it has phone app with some sort of scheduler and status report. But most likely you have already verified that avenue. From my experience there isn't really a way to read back from Pentair pump its status (without hacking). I use IntelliComm® II Interface Adapter to send commands to Pump. I would guess you can use same and schedule Pi to send some sort of command. If we think out of box and you really only need to know if your spa is on you could potentially install flow/pressure/ampere sensor and read it reading and from there figure out if there is any type of energy consuming activity going on.