Not a bad idea, but the bitcoin network is working against you. It silently buries all evidence of double-spend attempts. Here is data from one node that publishes the re-spend attempts that it sees though.
http://respends.thinlink.com
http://respends.thinlink.com
Thanks for sharing the page.
Do you know what they represent?
Forget it, it is right in the bottom of the page.
