Hey,
Found the answer to my own question :)
You can indeed get a list of changes merged in the last n seconds from gerrit, via its http API. The first change merged into Wikibase in the last 10 seconds can be obtained as follows:
https://gerrit.wikimedia.org/r/changes/?q=status:merged+project:mediawiki/ex...
Relevant docs at
https://gerrit.wikimedia.org/r/Documentation/rest-api-changes.html#list-chan...
and
https://gerrit.wikimedia.org/r/Documentation/user-search.html#_search_operat...
Cheers
-- Jeroen De Dauw http://www.bn2vs.com Don't panic. Don't be evil. --