Virtual On/Off Devices are meant to implement a simple parallel to a non-dimmable light switch (or appliance module). Therefore, it has a single "on state" represented by ON and OFF (not by any other values such as home/away) and controllable by the standard UI's that Indigo presents. If you don't want to use the standard Indigo controls to operate the device (the UIs and turn on/turn off/toggle actions) then this is not the right device for you (in fact the first sentence in the docs regarding those devices explains it well: "people who want to create a device that can be turned ON and OFF").
What you're looking for I think is some kind of custom device which has custom states (and custom values for those states) and some way to set those states. That is a completely different kind of device because it's a completely different use-case. Creating such a device, while possible, is a pretty big task to get right. It's not currently on our radar but I'll add a request to our list for future consideration.
I think I'd just create a variable for each phone and manage the values as necessary.
[MODERATOR NOTE] Split from another topic since the originating topic was about Device Groups (not Virtual On/Off Devices) and moved to the right forum.