P.S. in my recommended API, and despite what I said above about preferring explicit kwarg invocation, a "just the port" use is one spot where I could see users using just-an-arg:

``` python
with remote_tunnel(8000):
    # stuff
```

because that's very clearly unambiguous in my opinion -- it says "Within this block, forward port 8000 from my target to my localhost". That is (AFAIK) a common use case for this kind of reverse port forwarding.