Estimate location and speed of moving sound

I have a plan to install a pair of microphones on the corners of the front of the house and connect them to the computer to estimate the location of a given noise on the lawn. Given the distance between the microphones and an estimation of the speed of sound at our altitude, I should be able to measure the time delay between the waves and estimate the distance.

It will probably be harder to pick out distinct events in the wave form when the noise is generated by traffic, but it would be cool to estimate the speed of cars or trucks going by.

There are plenty of fancy multi-track recorders for linux. ( http://en.wikipedia.org/wiki/List_of_Linux_audio_software) Those might not give me the ability to measure time delays very accurately. Perhaps I need something more like an oscilloscope...

I'll also need two microphones with long cables and an adapter that will merge the two mono recordings into the stereo input jack on the computer. Perhaps something like this:

http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?item=SP-MINI-2

 Description:
24K gold-plated connectors • Accepts two 1/8" mono phone plugs wired "dual mono" 
(tip and ring connected together) • Fits 1/8" stereo phone jack • Lets you connect 
two dual mono or two stereo devices and send them to a stereo jack. Note: you cannot 
plug mono male plugs into this adapter!

So I need to have microphones that are wired "dual mono" to prevent shorting out the sound card circuit. That probably isn't too difficult to find. The extension cords will probably be the most expensive and hopefully I won't lose too much signal over the length of the cord. Probably will need 20 to 50 feet depending on how much I want to drill holes in the house.