Is there anyway for you to display which mining pools have seen and are relaying a particular transaction?  You could then calculate a rough estimate of how much hashing power (and what percentage of the total known bitcoin network) was aggregated behind an unconfirmed transaction.  Imagine a table with the major mining pools, their hashing power, and a simple yes/no if they are working on a given version of a transaction.  The chance of a double spend after all the major mining pools are working on a particular transaction would be slim to none.

This information could help implement Satoshi's suggestions to the so-called "Snack machine problem" and significantly reduce any risk associated with accepting a unconfirmed transaction (http://forum.bitcoin.org/?topic=423.msg3819#msg3819).

Here are some of my posts on the topic:
https://bitcointalk.org/index.php?topic=19481.msg253928#msg253928, and particularly
https://bitcointalk.org/index.php?topic=19481.msg254559#msg254559