Sometimes you start to test the networks around you for flaws , but you never really know from who is some wifi network .
Using a laptop and going around the street is too much obvious , but a phone no one will notice .
I think it is practical for people that want to know how far their wifi goes .
The android program i used is called : WIFI Map Maker (paid version)
For this to work you need to have a phone with GPS embedded and wifi , without those it will be impossible for the program to work , or even get the coordinates and start map wifi networks .
Snapshot from android phone (wifi map maker)
exported to Google earth as klm file :I never used kismet wireless to start mapping wifi , but i am planning to get a google nexus 7 tablet , install kali nethunter and try kismet wireless to start mapping with linux in future to see if it is pratical .
Google nexus 7 have a chipset that can be enable to work in monitor mode , this way you can use aircrack package and reaver wherever you go .
Here it is some links explaining how to configure your linux and kismet to start mapping :
http://www.wirelessdefence.org/Contents/Kismet%20Wireless%20Mapping.htmhttp://flylib.com/books/en/3.472.1.70/1/https://www.altamiracorp.com/blog/employee-posts/wifi-mapping