Netwatch with device on different subnet

Is it possible to monitor a device if it is not on a subnet in the router?

We are using just add power video distribution. They use static ip addresses not assigned or even in the router.

Is there a way to use netwatch to ping these devices even though they are on a separate subnet not in the router?

They are not in the router on purpose. There is too much traffic and it would kill the network.

Thanks.

Why not ?
Netwatch is just a ping + two scripts attached to it.