Not an answer but the Infratech 14-4400 Single On/Off Switch is ridiculously expensive at $103. Any of these would accomplish the same thing for far less:

• Leviton R52-0CSB2-2WS 20 Amp Commercial Double-Pole Toggle Switch ($8)
• Leviton 5622-2W 20 Amp Decora Plus Commercial Grade Double Pole Rocker Switch ($26)
• Eaton CSB220W-BX-LW 20-Amp Double Pole Toggle Light Switch ($8.50)

Wiring diagram.

You can get a heavy duty 40 amp smart switch at the power source and if the heaters stay in the last mode they were when the power was turned off you can use one. Depending on the amperage you could put at least 2 on one switch.

This is the one I use for my heated cement.

That Aeotec device looks like an excellent solution; one would need a device for each heater. But at $106 each, that would still be a bargain. To control the heaters remotely as the OP requested, the Smart Switches would need to be linked to a Z-wave hub (Aeotec example).