It looks like you need to add your paramters to the body of your request using.
$r->setBody('[{ "email":"m@addy.co", "password":"foo*bar!", "name":"addy-dev" }]');
As long the other side receiving will process the parameters sent in the body, this should work, otherwise it wont.
You may also want to send your request as JSON by adding the following line(Not sure if requirement).
$r->addHeaders(array('Content-Type' => 'application/json'));
EDIT: fixed syntax error of addHeaders.