I started writing one for iOS, using a game engine to get some really rich effects, but JIRA changes very quickly and I always found myself in their web interface rather than using what I had written. I am in the Atlassian ecosystem myself.
Honestly probably not as all client interfaces I've tried end up lagging behind the web or not having all the features. It's a huge undertaking to recreate JIRA in a client.
Someone would as there's already an app for that (<a href="http://almworks.com/jiraclient/overview.html" rel="nofollow">http://almworks.com/jiraclient/overview.html</a>) and it is doing fine :-)