The Nikon 1 Series is what your looking for, Nikon V1 or J1, and I think there is a J2 out too, but I think the V1 is what you will want. However the mount is different, but I think you can get an adapter.
From what I have read, the Olympus OM-D is a really sweet camera, I've considered one myself to have another smaller system on hand, but couldn't go for it because of price and I have a perfectly good Nikon D5100.