Amazon's Alexa voice control platform continues worming its way into more products today with the Onvocal OV Bluetooth headphones. The OV is like any other Bluetooth device in that it can communicate with the voice assistant built-into your phone, but there will be an app for OV that adds one-touch access to Alexa as well. That ability doesn't come cheap, though.
While Google's voice commands are more impressive in a myriad of ways, Amazon has been pushing Alexa on developers for longer. That has resulted in more than 5,000 "skills" for Alexa including Lyft, NPR news, SmartThings, Kayak, and more. So, there are reasons to prefer Alexa, but OV is currently your only option if you want Alexa on your phone.
OV has an unusual design. There's the u-shaped section that rests on your neck, and the right bud has a microphone that extends in the direction of your mouth like a phone headset. It's probably better for voice commands, but it looks a bit old-fashioned to me. OV is available for pre-order now for $399. It's expensive, and oddly is not listed on Amazon yet. It will start shipping in January.