Hi mweston,
If you are unable to connect to your external IP from within your network, then it would appear your router does not support NAT loopback (see
http://en.wikipedia.org/wiki/Network_address_translation#NAT_loopback)
Remembering IP addresses as well making logging in simpler are things we would love to add in a future release of the app.
In the meantime, a user reported a work around by adding his IP address into the autocorrect dictionary on his phone so that he only had to enter the first couple of numbers.