Even if you were able to find a native application for Mac, I think you would still have to go through IB's API client or Java-based TWS. I don't know of any application aside from TWS that directly connects to IB.
www.linnsoft.com investor r/t has a native mac version that will take data from IB and let you send orders to IB.
IB FIX. you can use the 2400+ pdf that explains in torturing detail how to design a front-end application for use with them.
I was not referring to the FIX being torturous, but the action of having coding a front-end application that does more than the fluff that is provided by 99% of brokers.