YES, there IS. It's called MagicBeans, and was released on 9/25/2009.
It's been in development since 06/09. It adds a whole lot of features for
the magicJack, including Call Block via CallerID (aka: Caller ID), ring-duration
controls, active call forwarding (not MagicJack's offline call forwarding website), and lot of other neat additions to magicJack.
The website is http://www.magicjackbeans.com
MagicBeans is currrently intro priced at $12.95 (MSRP $19.95).
Hope this helps!