Hi there,
I had a bit of a hiatus - sorry for that! - but I decided to announce the client today! I wrote a README and pushed the code to GitHub: https://github.com/mbork/beeminder.el . I also wrote a post on my blog: http://mbork.pl/2015-08-22_Beeminder.el .
As I wrote, I now submit most of my datapoints using this client, to the point that even the Android one (which is much better than the web one) feels clumsy to me.
Currently, there is no Org-mode integration, but I’m going to add some soon.
Please try it out and send me bug reports/feature requests!
Good luck beeminding with Emacs!