Floating the probes in foam will not increase or decrease their susceptibility to interfere with another. Floating the probes results in a longer life and more reliable probe operation since one possible failure mechanism has been eliminated.
What are you thinking in the way of wireless pH probes? A monitor/controller that has multiple wireless pH probe modules? Not sure why you would really want wireless controller as it would appear to be a less reliable option than a hardwired probe.
I'd love to add Ca probe input to our controllers. Unfortunately, there still isn't a Ca probe available that is reliable and low maintenance enough for continuous use. From what I've read and seen on the PinPoint Ca probe, it takes longer to get an accurate measurement than performing a standard Ca test. The probe goes out of calibration quickly, has a huge temperature variation, can't be used continuously, etc. I don't think it is ready for the average aquarist yet.
Curt