I checked out the latest version of caliper and ran a few benchmarks. The result are generated (as json) just fine, but upload to the microbenchmarks appengine website fails with:
POST http://microbenchmarks.appspot.com .... returned a response status of 405 Method Not Allowed
This issue has been raised with the Caliper team already: https://code.google.com/p/caliper/issues/detail?id=220
... but was closed as "invalid". So I assume there is an alternative way to upload results ?