Can you use the app where s my iphone if?

If the device youre trying to find (iPod) doesn't have that app?

No because then it isn't registered with it in settings.

Yes, but only if the both devices are actively connected to internet, be it wireless service providers, Wi-Fi or ethernet. If the "start" device, the one that is displaying where the ipod is, isn't connected to internet, the page will only show the last known position. If the ipod is not connected to internet, the start device will, again, only show the last known position. The app is only if you want to use your ipod/iphone/ipad as the start device