OK so here are the ones I've used in the past:
Streampro.io (they have an Extra Life integration, still seems to work although I'd seen mention they no longer support EL): Here's an example of an overlay I built https://streampro.io/overlay/5604ef0df9261411093bb2a7/DZlXUxzKXS7zA4YYz0MoOCH7vSdqRG6K
If Streampro doesn't work, use Streamlabs.com - goodness it's changed a lot since I last used it. Looks good though.
An app built by a fellow Extra Lifer! http://community.extra-life.org/forums/topic/404-extra-life-helper-show-real-time-donation-info-on-your-stream/
Another app built by a fellow Extra Lifer! I use this one the most because it can output just text files, which you can then use in a variety of ways through your streaming software. Once I figured out how to install the Furore font on my computer this was the best way to go for me. http://community.extra-life.org/forums/topic/2726-my-extra-life-stream-helper-v069-1132016-custom-imagesound-alerts-text-file-stats-output-team-info/
Generally you're looking for cool ways to show your amount raised, possibly your goal and then how to display donation alerts. Hope these help!