This probably isn't the most helpful, but I use a Wahoo TickerX which has both Ant+ and Bluetooth connectivity, and it works fine with the Pixel. But I have no way of knowing if it is connected via Ant+ or BT. If I had to guess I would say it's BT, I always thought Ant+ was more for commercial grade exercise equipment (like you can sync your heart monitor to the treadmill at the gym).