It took a whole day in front of an ssh screen onto my server to get Kannel up and running, but I finally managed to get a box ready to be tested.
A very useful resource is the SMSC emulator from Selenium Software. They're kind enough to give it away, and it is definitely the pick of the litter compared to the other free options.
I needed this because for some reason Kannel wasn't liking the fake SMSC setting. I had noticed that the binary file they refer to in their documentation was missing from my install (a Debian apt-get install kannel default). So I thought I would rather emulate an SMSC than fiddle with trying to get the fake one running.
I had a few errors that were baffling due to the lack of thorough documentation, but the email@example.com list (subscription needed to send to it) was awesomely helpful. Within an hour of posting my config files and outlining what I had tried I had a solution thanks to a tip from them. The mailing list is searchable so it can take the place of trouble shooting documentation in my opinion.
What worried me was that the default example config file that Kannel distributes did not work out of the box. I had reverted to using it after my handcrafted config was spitting "smsbox_list empty!" warnings on the bearerbox.
Fixing the "smsbox_list empty!" problem
In any case fixing the "smsbox_list empty!" warning for me was just a matter of sending an SMS through the smsbox. Kannel does not recognize an smsbox as being routable until it has been identified or had an MT sent from them. I had seen the logic in the bb_boxc.c code, but needed a Kannel guru to interpret this for me.
It's just a question of having the proper routes and services set, which for a test installation is easy to do using the Kannel documentation.