I have one that I mentioned somewhere else and someone actually gave it a go, not sure how it's progressing or they gave up on it or what.
An advanced ear plug alarm clock. Think about it. I'm not married but I bet one of the biggest complaints of sleeping with someone else every night is some type of noise they make, so just use ear plugs, right? Well, then you can't hear your alarm. Also, I'm sure many partners are woken up by the others alarm when they don't need to wake up til hours later.
My idea was somewhat of a bluetooth ear plug alarm clock. You can connect up to two pairs of earplugs to a device where you set the alarm time and other settings. Basically the alarm is a slight ringing noise (wouldn't have to be loud/disturbing as it's in your ear) that plays through the earplugs, it can ascend in loudness so it wouldn't startle you or anything. Also, another worry might be if a fire alarm went off, or a window broke and a burglars entering. You can set the sensitivity of the alarm for certain noises to play through the same speakers that the alarm goes through, but that's a whole other dilemma I haven't completely figured out yet.