A Comma 3 to run Openpilot on my Honda Civic. It's lane keep / adaptive cruise control on steroids. I drive about 40 thousand miles each year for work, 46 miles round trip on "local" days. Having that level of driver assist on the highway makes a life changing difference. I arrive less fatigued and feel more capable of reacting to hazards. Their tagline is making driving chill, and it really has delivered. I don't know how I did this mileage before Openpilot.
It's considered a "level 2" driver assist, enhancing the existing adaptive cruise or lane keep assist built into the vehicle (which are also considered level 2 and perfectly legal) The driver is still completely responsible for anything the vehicle does.
That said IANAL, but I feel comfortable with this level of vehicle modification and any liability involved.