SRV records can be used to declare the backend nodes; just use the -srv-domain flag.
dig SRV _etcd._tcp.confd.io
...
;; ANSWER SECTION:
_etcd._tcp.confd.io. 300 IN SRV 1 100 4001 etcd.confd.io.
confd -backend etcd -srv-domain confd.io
dig SRV _consul._tcp.confd.io
...
;; ANSWER SECTION:
_consul._tcp.confd.io. 300 IN SRV 1 100 8500 consul.confd.io.
confd -backend consul -srv-domain confd.io
By default the scheme is set to http; change it with the -scheme flag.
confd -scheme https -srv-domain confd.io
Both the SRV domain and scheme can be configured in the confd configuration file. See the Configuration Guide for more details.