Yes! We have one, it's called the Oracle by RSF (Canadian company). We love it. We have used it a couple of times this fall and it has provided a nice heat for the 2 story living room and large kitchen it sits between - and the house isn't even finished yet!

Here is a link that might be useful: check out the Oracle here

The Oracle is not what the OP wants. He wants an insert for an existing 2-sided open fireplace, which as far as I know does not exist.

greg, xanndra is correct.

http://www.hearth.com/econtent/index.php/QA_Templates/info/294/

However, that is not to say that it cannot be done. If you know a GOOD metal fabricator, are willing to pay thru the nose for its construction, are not subject to EPA phase 2 restrictions where you plan to burn the insert, & have the approval of your mortgage & insurance companies, then the answer is yes.
And please post some pics of it in operation.
Thanks

hi greg,
did you ever find a gas insert for your double fireplace?
thanks,
marilyn

This is an old thread, but just wondering if anyone has found a two-way insert. We are looking at buying a house with an existing double-sided fireplace with gas logs between the family room and living room. It looks great, but I am concerned about heat loss. The fireplace inspector had recently installed a double-sided ventless log set in another home, which he recommended, but I am leery of ventfree products in general. I would love to find a way to make it direct-vent gas. (Prefer not wood burning-I find it messy, smelly and a hassle.) Any other options?