Make 'number of obfsbridges' metrics graphs
It's currently possible to get the number of bridges that support obfs2/obfs3/etc. using sanitized bridge descriptors (https://lists.torproject.org/pipermail/tor-talk/2012-December/026878.html).
Maybe a metrics graph showing the number of obfs2/obfs3 bridges over time would be interesting.
(Sorry if I filed the bug in the wrong "Metrics *" component.)