Except it wouldn't work. If Fitbit is collecting my data, and I'm not intending a breakup, then my heart rate now is independent of what my partner will be doing or saying in five minutes when they break up with me. It'd only really be useful if it collected your partner's data and fed it to you.
However, you'll see similar spikes from your partner before any major relationship event. They want you to meet their family. They need to tell you they can't stand your mother and her overbearing nature. They want to move in together or propose. All these would likely look the same (modulo degree) to Fitbit.
Given that these gadgets will probably all be location aware, I'm pretty sure the company[1] can figure out who you're dating and what stress they have. Basically, triggering your reaction to the breakup will probably get a search on what your former significant other was feeling and the data processing would probably happen from that end.
I really don't want to deal with that world.
1) both people need to be using the same device, but that's probably more common than not with peer groups. Lord help us all if they come up with a standard exchange protocol between devices. The alert "Hey, the dude entering the room now is really mad" is going to set off all kinds of hell.
Again, though, it only indicates that your partner is stressed, and potentially that they're stressed about the encounter they're about to have with you. It doesn't measure enough (assuming there's enough to measure) to know the difference between "He's going to break up with you." and "He's been fired and doesn't know how to tell you."
I would imagine that's true in the current iteration, but I'm not so sure it will stay true. I'm also not sure how much external data they can get their hands on to start looking at connections with other parts of your life. Target's little snafu with telling a father his daughter was pregnant has made me think a lot more about sensors combined with big data.
That's a fair point. A lot of behavioral data can be gleaned from collecting someone's shopping habits, browsing behavior, general communication trends on various platforms (directed or not to their partner).
The heart rate and biometrics would perhaps let you know the when of the event, then, and not that it was on its way. The same predictive techniques could work for other events as well (has he been buying a lot more home goods recently? maybe he's about to ask you to move in).
However, you'll see similar spikes from your partner before any major relationship event. They want you to meet their family. They need to tell you they can't stand your mother and her overbearing nature. They want to move in together or propose. All these would likely look the same (modulo degree) to Fitbit.