If monitoring the ISM bands was illegal, wifi would be illegal. Wifi stations continuously monitor the channel they are using to avoid interference and will ty

If monitoring the ISM bands was illegal, wifi would be illegal. Wifi stations continuously monitor the channel they are using to avoid interference and will typically monitor the whole band during the frequency selection process (i.e. searching for the least-crowded channel when setting up the AP). The fact that the ISM bands are basically a free-for-all is one of the best regulatory moves in the history of radio, since that has basically made the diverse market for wireless consumer electronics possible (including wifi and bluetooth, two of the greatest inventions in consumer electronics in my lifetime).