SPITFIREFOX is based on nCoAP.
The following screenshots (from a virtual Nexus 5 android device with API 23) exemplarly show a request to coap://vs0.inf.ethz.ch/obs
and the response.
The Response Fragment on the right is to display the response of the server. To save space, only options that were present in an incoming response are displayed in the response fragment. One can switch between both fragments with a swipe.
See also: coSense - A CoAP Server for mobile Sensors attached to Android devices