Valuations in the med-tech space lately call into question the old medical adage: “If you hear hoofbeats, think horses.” These days, you would be wise to consider unicorns in the differential diagnosis. Two new companies achieved the formerly rare status just this week. Viz.ai Inc.’s closing today of a $100 million series D financing propelled it into the stratosphere with a $1.2 billion valuation, joining Bostongene LLC which completed its own $150 million round Wednesday.