I didn’t deploy any object detection model with Pytorch but from docs and app code, Pytorch Mobile should work fine with these type of models. The only limitations that I’m aware are the missing support for nms and roi_align torchivision operations (see post 21). I think that TFLite doesn’t support NMS. So, a mobilenet + ssd/ssdlite head or similar  should work fine.
That said,  It would be nice to have some reference implementation. At least, to view the predicted bbox.
If you are worried about pytorch performance, you may want to take a look into this issue 8. I found that Hello World App performance to be much worse than Pytorch Demo App. Demo App runs nearly as fast as TFLite under the same conditions without any hassle 
Finally, last month I was searching for mobile object detection models and I found DiceNet. It’s interesting and researchers have used Pytorch.