I think that the HTTP API can support GET or POST methods, but I've only used the GET method myself. With the newest systems (like TC-AE2, TC1, VMC1 or 3P1) websockets are supported which is the best way to go for this.
I'd love to test Panamation with a 3play for clip control (pause/play/jog etc.) I don't have a copy of 3play so a free copy of panamation to someone who can do the test and record a screen grab of it! PM me for details.