There are a couple of things you can do here:
- Do call forwards with particlular timer periods, so that the call forward will ring the appropriate number for the time in question.
- Have multiple VoIP devices registered in multiple locations with the same voxalot account.
The second option will ring every ATA device for your single Voxalot account. And in order for your cell to work, it needs a VoIP client installed too.....