In theory this should work but I can't get it to so comments or suggestions appreciated.
If your Mac is connected to the Internet by ethernet you can create an ad hoc wireless network using its AirPort and then connecting your wireless device. This method is well documented.
I thought I might be able to do the same by tethering my iPhone to the laptop, creating a network, and then in Internet sharing setting it up so that it shares it from the iPhone to computers using AirPort.
In my test situation my iMac and a second iPhone are able to connect to the created network, but they're not able to access the Internet, with the iMac self-assigning an IP address.
This is where my networking knowledge gets a bit limited. I'm assuming that if it's not some sort of hardware limitation I'd need to manually assign the other wireless devices an IP within the same range as the created network, or somehow use the laptop [with the created network] as a DHCP server to assign the correct addresses to the other devices?
I've tried doing a Google search but can't find anything.