Arduino + GPS + Wifi + Cellular Wifi Hotspot and REAL TIME data

I am working a project where I can track the location of multiple vehicles and display there location in real time ( pseudo real time, updating every 5 minutes would be fine )

The vehicles already have wifi on board for other purposes, and I would like to take advantage of that.

There are plenty of tutorials out there including the one here which recommends the hardware http://forums.adafruit.com/viewtopic.php?f=8&p=265900

My problem comes in writing the data over wifi to a web server somewhere, and then interpreting that data and displaying the gps coordinates on a live updating map.

I've did some research and found a few examples that use GSM, but not any for wifi exclusively.

Do you think the hardware recommended in the adafruit link would be best or is there something newer/better I could use?

I'd like to keep this post updated as an ongoing review of the development.

Stage 1: Hardware Selection and ordering Stage 2: Soldering and Initial Configuration Stage 3: Local Data logging ( writing to SD card ) Stage 4: Connecting to Wifi and writing data to web servive ( like data.sparkfun.com or plot.ly ) Stage 5: Developing web server to receive data Stage 6: Take received data and publish to Google Maps in rea time

Any direction would be appreciated.