You're right! Ensemble forecasting is great! Vistimo proper (https://www.vistimo.com) does both -- it gets individual high/low estimates from multiple people, and creates a combined distribution from all of them (though each estimate is a log normal, not normal, since it's a time estimate).

But Vistimo is a full project management tool; that space is full and switching project management tools is expensive, so it's hard to get people to adopt.

Vistimo Quotes is a much lighter-weight way to get many of the same benefits without having to talk your whole team into signing up.