I have just released v1.2.0 of the Prometheus Pushgateway.
In addition to internal cleanup of the HTTP routing code, this release adds a new JSON HTTP API to query runtime information and the pushed metrics in the grouping used for pushing them. Essentially, all the information in the web UI is now accessible via an HTTP API, which enables easy integration of this information into other UIs, scripts, etc. See the relevant section in the README.md for details.
Special credit goes to @drumilpatel2000, who did all of the work.