The Wi-Fi Hotspot app included with the Nokia N9 provides an easy way to get laptops, etc. connected to the Internet. However, much to the disappointment of N9 users in the United States, all that appears is a "Not allowed" error when connected to a US mobile phone network.
This error is due to ad-hoc wireless being disabled, apparently due to Federal Communications Commission limits on RF radiation output that are stricter than other countries. ad-hac eliminates this restriction, making it possible to uplink worldwide via your phone's data connection.
While ad-hac is mainly intended for those living in the US, world travelers should also find it useful. ad-hac has no effect when your N9 is used in other countries.
Warning: Staying compliant with FCC regulations is your responsibility. If you get taken away to a secret underground FCC prison, or grow a tumor on your ear, this is your problem.
Compatibility: If you added an Upstart job or other tweak for enabling ad-hoc wireless, it's recommended to remove it before installing ad-hac. ad-hac does not interfere with SpotOn, which toggles ad-hoc wireless on and off - however, since ad-hoc wireless is always enabled with ad-hac, there's no need for a toggle.