Marriott fined $600,000 by FCC for interfering with customer WiFi hotspots
Marriott (since 2012) has been using wireless technology to prevent guests at the Gaylord Opryland hotel and convention center from using their own Wi-Fi mobile hotspots, forcing exhibitors or customers to use Marriott's expensive Internet services, available at the whopping cost of $250 to $1,000 per wireless access point. Despite popular press reports, this did not involve "jamming" which is strictly illegal in the US, but instead something more like a WiFi DoS attack.
Marriott had deployed a Wi-Fi monitoring system with a "containment capability". When activated, the system could identify Wi-Fi access points that were not part of Marriott's own Wi-Fi system (or otherwise authorized by Marriott). Such non-Marriott access points were dubbed "rogues". When rogues were detected, the system sent "de-authorization" packets to the unauthorized access points, booting those users off their free connections and, presumably, forcing them to pony up for Marriott's paid Internet access.
http://www.commlawblog.com/2014/10/articles/enforcement-activities-fines-f/marriott-whacked-for-600000-for-war-on-rogue-wifi-hotspots/
Marriott had deployed a Wi-Fi monitoring system with a "containment capability". When activated, the system could identify Wi-Fi access points that were not part of Marriott's own Wi-Fi system (or otherwise authorized by Marriott). Such non-Marriott access points were dubbed "rogues". When rogues were detected, the system sent "de-authorization" packets to the unauthorized access points, booting those users off their free connections and, presumably, forcing them to pony up for Marriott's paid Internet access.
http://www.commlawblog.com/2014/10/articles/enforcement-activities-fines-f/marriott-whacked-for-600000-for-war-on-rogue-wifi-hotspots/
Other than the firmware mods (which I gather aren't actually available unless one writes them) your other suggestions are of course untenable.
Starting to seem as if the better approach would simply be a 3G card or dongle directly on each device, removing 802.11 from the picture. This works with most family plans. Pity though, having to spend extra money to dodge the bastards. Of course on their premises they could conceivably jam GSM and CDMA too.