There is the ROCKBROS helmet with built in lights BUT THOUGH THE DESIGN IS NICE AND CLEANLY INTEGRATED, THE PRACTICAL FUNCTIONALITY OF THE AVAILABLE FORWARD BEAM OF THE HEADLIGHT PROBABLY IS NOT ENOUGH TO SATISFY NIGHT RIDERS WITHOUT SOME OTHER ADDITIONAL FORWARD FACING HEADLIGHT ON THE BIKE. (see the YOUTUBE link below)
https://www.walmart.com/ip/ROCKBROS-...hite/348159922
https://www.ebay.com/itm/124879449498
I believe that bicycle mounted headlight(s) offer the best overall lighting option BECAUSE you can by how you position them when mounting them will allow you to project the light beam forward in the area ahead exactly where you want and need the light to be precisely focused for maximum road ahead visibility. LIGHTING ON THE HELMET ALONE MAKES YOUR HEAD NEED TO BE OR MOSTLY REMAIN IN A POSITION WHICH MAY NOT BE THE MOST COMFORTABLE. EVEN IF YOU DO GET THE LIGHT MOUNTED IN WHAT IS A COMFORTABLE POSITION, YOU MAY GET IRRITATED FROM THE INABILITY TO VARY HEAD POSITION & ANGLE, IF ONLY TO KEEP FROM THE FATIGUE OF TRYING TOO MUCH TO BE LIKE A STATUE OR MANNIQUIN TO ENABLE THE LIGHT TO FOCUS PRECISELY FORWARD IN THE BEST OVERALL PATTERN. Some folks don't like the idea of a headlight being physically mounted on the bike because it looks too "Fred" or uncool like something a Huffy, Schwinn or Wallyworld bike owner might affix to their bikes. Who gives a - - - - about that because it is about keeping you ALIVE & SAFE, so you can see the road ahead at least better than Mr. Magoo. If you think it looks goofy, well remove it when you don't ride at night & re-install when you DO NEED to ride at night. You all know this but it is worth repeating: IT IS BETTER TO HAVE TOO MANY HEADLIGHTS ABOARD YOUR BICYCLE AND ONLY USE THEM AS YOU NEED THEM, RATHER THAN NOT HAVE ENOUGH (INSUFFICIENT) HEAD LIGHTING. If you have enough aboard, you might not need to turn them all on, but it ain't such a great ride when you've only got ONE aboard and its fully lit and there is no moon out and the street has no streetlights, and you are at that moment wishing you had at least one more light on your bike....