HTTP API can be used to integrate 3rd party devices, which support access through HTTP protocol. Devices usually act as a WEB server. There is necessary to find IP address or hostname of the device.
For devices used in local network please use programs for finding device IP address like Android application Fing (https://play.google.com/store/apps/details?id=com.overlook.android.fing&hl=en_US).
For devices with known host name you can use browser to copy the hostname and relative path to the device definition.