The trickier problem is the wireless receiver itself. With many wireless chipsets merely listening for incoming packets takes nearly as much power as actively transmitting or receiving does.There are many micro processors that are normally asleep until woken up by a stimulus ( from a wireless receiver ) , perform what ever function is needed and then go back to sleep.
Theres a reason low end wireless burgular alarms are usually one-way communication.
You have to read the datasheets carefully though. For example on the PIC18F45j20 I used in a low power battery powered projects you only get the lowest power sleep mode (which the headline figures reffer to) if you have the main memory disabled (so you basically have to reboot when you wake up) and all the timers disabled so you can only wake up on external triggers.SimonH2 said:There are certainly processors which take a matter of nW in sleep modes.
Microwatts is more typical for a useful sleep mode with main memory retained