My guess is that most locating apps work using location services. Location services works by either triangulating the cell phone over cell connection or GPS. The iPod does not have a GPS or cell radio in it.
I have heard of location services using WiFi location, but then you would need location services installed and my guess is that it is not installed on the iPod. However, if it is, then you could connect to WiFi, turn on location, download an app to find your device, and then find it over WiFi. But accuracy is going to be hindered greatly using location over WiFi. Not to mention you would have to have the WiFi radio on to even find the device in this scenario. Which is impractical and not a good idea for good battery life.
Another option would be an app that when activated turns on the speaker of the iPod and beacons. But you would need a way to remotely turn this feature on. The only options here are Bluetooth and WiFi. Again the idea is hindered by needing one of those two radios always on. Which is impractical.
Probably the best options is one of those key finders. Key Ringer (http://www.keyringer.com/) is one such company. But the downside is you will need one of those bulky devices always attached to the iPod.