KisMAC is a free stumbler application for MacOS X that puts your card into monitor mode. Unlike most other applications for OS X it has the ability to run completely invisibly and send no probe requests.
KisMAC supports several third party PCMCIA/PCCards cards with Orinoco and PrismII chipsets, as well as Cisco Aironet cards. AirPort and AirPort Extreme cards are supported in full passive mode, as well as Prism2 and Ralink USB devices.
These details are provided for information only. No information here is legal advice and should not be used as such.