I'm pretty confident that every single product manufacturer has some sort of Wi-Fi hotspot locater available. And generally, they all equally suck: an LED comes on when it finds a signal, then you are forced to bust out your laptop or PDA to determine if that signal is even worth using. The iRock Wi-Fi sentry has taken the Wi-Fi locator concept and made it a little more useful. Bottom line, this thing is directional. Push the button and it will light up if a Wi-Fi signal is in range, and it also shows the signal strength. Even better, move it around to find the source of the Wi-Fi and to get a better signal. Only downside is the inability to determine if a signal is encrypted or not. Twenty bucks via the iRock product page.
iRock Wi-Fi Sentry [Mobility Today]