Good PDA Wi-Fi Signal Strength Locator?

Tark asks: "I have been tasked with creating a reliable, portable 802.11b signal strength indicator. I have looked over various PDA's, and have narrowed it down to two: the Sharp's Zaurus 5500 Linux PDA, and the HP iPAQ 2215 Pocket PC. I have chosen these due to the fact they both support cf and sd slots. Which of these 2 PDA's will provide a reliable solution for detecting an 802.11b signal, and which wi-fi card should I use with the PDA? Also, is there a CompactFlash wi-fi card that supports a external antenna connection?"