צָפָה / Tsapah
Mizpah comes from the root word צָפָה / tsapah, which is used frequently through the Tanakh to speak of 'watchmen' or otherwise keeping watch over things. Unfortunately this is the only occurrence of the word in the Pentateuch, and so we have to rely on later usage for its meaning. Thankfully later usage is clear and consistent:
Now the watchman (וְהַצֹּפֶה֩) was standing on the tower in Jezreel, and he saw the company of Jehu as he came and said, “I see a company.” - 2 Kings 9:17a (ESV)
For thus the Lord said to me: “Go, set a watchman (הַֽמְצַפֶּ֔ה); let him announce what he sees" - Isaiah 21:6 (ESV)
Seeing the given usage of 'Mizpah' in the Tanakh, it would appear to be invariably a place name (for two or more locations), and one which becomes prominent from the time of the Judges onwards. Given the way the name is set up in your given Genesis passage, this isn't surprising:
It was also called Mizpah because he said, “May the Lord keep watch between you and me when we are away from each other..." - Genesis 31:49
Whilst the spoken tone is defensive and semi-confrontational, I think it would be a mistake to read this into all usage of the word.
Context of Mizpah in the Tanakh
It seems significant that a Mizpah (whether the same location or otherwise) would become a typical rallying place for Israel, a place where it had been proclaimed "the Lord is watching". It's the place where all Israel gather to pronounce judgement on the tribe of Benjamin (Judges 20:1), it's the place where Samuel set up his seat to judge, and later appointed the King (1 Samuel 7:6, 10:17), and even Gedaliah later set up the seat of Judah in the early days of the Exile (Jeremiah 40:10), when Jerusalem had been destroyed.
Even in your questioned usage from Genesis it's not an entirely negative term, but seems somewhat neutral - it's not 'God is watching you', but rather 'God is watching us', and Laban makes this clear:
This heap is a witness, and this pillar is a witness, that I will not go past this heap to your side to harm you and that you will not go past this heap and pillar to my side to harm me. - Genesis 31:52
In view of your question, I'd say its early usage is more in line with 'God is keeping watch' rather than 'truce/treaty between near-enemies'. It's certainly a truce between them, but seems to be on the basis of 'let God keep watch over us' rather than them keeping watch over one another. The frequency of its later use suggests the people considered it as a place where God could be sought to bear witness to things, rather than a place to gather when seeking judgement or vengeance from him.
Towards modern usage
This fits well with the usage you're asking about, where God is to watch over two or more parties in a positive sense. I don't think an 'emotional bond' is a great way to describe it, but the concept of such a pendant bearing those words of 'may the Lord keep watch' seems to be a fair usage of the phrase, albeit in a very different context to Laban and Jacob.
Yes, the quote is being taken out of its context, and won't naturally be read by others in its correct light, but at face value the way it's being understood isn't necessarily a bad way of understanding the phrase. Given the usage of Mizpah throughout the Tanakh, such a modern usage seems to be fair and in-keeping with the term's wider usage.