Check this out!
Wifi Meter
It will not do WPA but it can do 64 and 128 bit wep. You can program target IP's to ping, it will show you a very good signal strength display and I have used it to find dead/ weak zones around my house.
This used to sell for 219.99 Fry's is not going to carry it so its at 99.99.
Runs on 4 AA batteries and is very light