Good news! This can already be accomplished in a number of different ways.

You could create a Contact condition to turn the volume loud when your spouse calls. If you didn’t want that to always happen, simply add a Location condition. (I’m assuming you’d most likely want this feature while at home).

Alternatively, there are a number of third party plug-ins that could also be useful. For example, you could set up the SMS condition to detect a specially crafted SMS from your spouse which triggers an insistent Notification Plug-in setting.