I have since quit WoW, so I can no longer maintain this addon. Thanks to everyone who downloaded it.
Someone has taken the basic code and made a more complex and feature rich addon: http://www.wowinterface.com/downloads/info19608-myBigIgnite.html
Description
IgniteTracker is a simple addon to add an aura notifier for whenever Ignite starts ticking above a user-set threshold.
Use
Slash Command: /it
The addon is comprised of two components: The Ticker and the Notifier. To modify the ticker, use /it frame. To modify the notifier, use /it notifier.
The Ticker frame shows the last tick value of Ignite on your current Target.
The Notifier frame will pop up above your character when Ignite is ticking for a value above your set threshold.
To set the threshold, use /it notifier threshold X, where X is a number. When Ignite starts ticking for damage above X, the notifier will appear.
Future
I would like a different texture for this, but my texture work is marginal at best. If anyone would like to submit a texture, I'll credit you in the addon.
Patches
4.0.3.b - Corrected a bug where the addon was not saving the frame's location.
Licensing and Credits
This work is licensed under a Creative Commons Attribution 3.0 United States License. For more information: http://creativecommons.org/licenses/by/3.0/us/
Thanks to Colovick and Rickyjay of Korgath US for testing this addon.