You could initiate a IP camera ingest via curl as follows:
Alternatively, you can use the MediaCaster API and setup a HTTP Provider to implement it (such that you could invoke the http provider in a similar manner via HTTP).
curl --digest -u myuser:mypassword "http://[wowza-ip-address]:8086/streammanager/streamAction?action=startStream" --data "vhostName=[vhostname]&appName=[appname]/[appinstance]&streamName=[streamname]&mediaCasterType=[mediacaster-option]"
// You can also utilize action=deleteStream and action=resetStream accordingly (if/when needed). The mediaCasterType parameter would not be needed in the latter two cases.