My idea was to use multiple RTL8188CUS (Realtek Wireless Chipset, 802.11b/g) units to build a cheap WiFi stumble using Kismet without the need of hopping channels. If you do not hop you can scan more bands and capture more useful output when [http://www.wirelessleiden.nl/projects/heatmap wireless heatmapping].

The Realtek RTL8188CUS comes in many shapes and forms:


Pro:
 * The Linux driver is found at [http://www.realtek.com.tw/downloads/downloadsView.aspx?Langid=1&PNid=48&PFid=48&Level=5&Conn=4&DownTypeID=3&GetDown=false&Downloads=true#2742 Realtek Website]
 * Unit is cheap: [http://dealextreme.com DX] sells them for less than 5 EUR.

Cons:
 * The driver does not handle multiple cards at the same time.
 * No driver support for BSD derivatives. 
 * Kismet does not seems to support this devices.

Conclusion:
 * The units are currently not usable for the Wireless Heatmap Multiple Cards project.