I just got it to work on my Surface Pro (Windows 8). Detailed instructions
Here
Basically it puts your laptop between your 3DS and your router, allowing you to see exactly what information is passing through. Instacheck interprets that information and shows you Poke-info in a nice GUI.
Instacheck looks like this once you get it to work
http://i.imgur.com/SOqUneB.png
Delete the 3DS's remembered hotspot, then reconnect to the internet via the new one.
Click
Start Instacheck and this window will come up
http://i.imgur.com/6N4fkc3.png
Click
Start Scanning and do a trade online. The information will populate as seen in the second image.
Click stop scanning and it apparently crashes :lol
Trainer Name: Ray
SV: 348
Friend Code: 2578 3149 3873