I’m not exactly sure what you’re thinking of. Here are some possibilities. 
- Many people take a battery powered contact sensor that has dry contacts and add it to a nonnetworked device so that you then have a ZIgbee or Z wave radio that is triggered by that nonnetworked device. People use these for things like pressure mats, doorbells, Gate sensors in areas where the weather too harsh to put an RF device, and many other uses.
It’s pretty simple, you just open up the contact sensor and wire the other device to the dry contacts. After that the other device closing the circuit will register as on or off.
I will give you a link to a thread on pressure mats which is a good example. The same method can be used with many different kinds of devices.
- Another option which is commonly used for Mains-powered devices is the mimolite relay, which also has dry contacts. You will find much discussion in the forums on various projects where people have used it.
http://www.fortrezz.com/index.php/products/mimolite
- As far as the battery type device, the only thing that sounds at all similar is the roost battery which adds Wi-Fi capability to a smoke alarm. But that doesn’t seem general enough for what you’re talking about.
http://www.amazon.com/Roost-900-00001-Battery-Alarms-Single/dp/B00ZWQHVP4
- Finally, there is the SmartThings ThingShield which is used to add a SmartThings – compatible zigbee antenna to an Arduino board and which can then be connected to many different kinds of devices. This is the one people often use if they’re trying to hack a more complicated device like a remote control of a different protocol. It requires some definite maker skills, though.
Is any of that getting close?