Backstory: Recently I saw a facebook post of someone joking about the loud volume in their car in the morning, they mentioned their "morning self not being ready for the loud volume of last night." I chuckled because I've done this before.
The Idea: An adapter or integrated solution to car radios to adjust the volume based on time of day.
Deep Dive: This one is pretty simple, similar to monitors dimming the color at night and cars increasing the volume at higher speeds. Why not automatically reduce the volume in the morning?
You would have to build a simple piece of hardware that would learn user's habits and schedules to adjust the volume to minimal levels in the morning.
Validation: Both a friend on facebook and myself have run into this similar issue.
Monetization: You would have to figure out what the market would pay for this piece of hardware and charge accordingly. I don't see how this would turn into a SaaS but you could turn at profit at 60-70% margins if people are willing to pay.