According to http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.7, DELETE method should identify resource to be deleted by Resource-URI.
Methods should not require a application/json formatted body. Note that clients are not so strict here, but some of them simply turn request to POST if body is present. Some of them does not allow DELETE to include a body.
Current API also duplicates data, for instance pushApplicationID is both part of URI and JSON body.
More discussions about topic here:
I'm marking issue as critical as it affects API we are trying to stabilize.