The AppFog command line tool is very straightforward and even somewhat Git-like: http://docs.appfog.com/getting-started/af-cli. If the "af" gem is installed, "af push" is the equivalent to a "git push." You're right that it's not the same thing, but it's pretty handy.
Extra runtimes (newer versions of Erlang, plus Perl, Go, etc.) will become available over time. They're high priorities for our dev team, as are Redis, Memcached, etc.
Regarding git vs af, if I could use the git already installed in my computer, and by simply adding my SSH key into AppFog system, I could avoid using `af` gem and Ruby altogether. Otherwise, I would have to install Ruby just for this purpose. But this is just personal taste.
Other PaaS such as Heroku or OpenShift allows you to set up a custom app. For example, you can create your own app type in Heroku's cedar stack with buildpacks, or the DIY app in OpenShift with supports for hooks.
Erlang probably isn't on the top of the priorities list, but I'm looking forwards to it.
Extra runtimes (newer versions of Erlang, plus Perl, Go, etc.) will become available over time. They're high priorities for our dev team, as are Redis, Memcached, etc.
What do you mean by "no custom app?"