I just got a HIFI Walker G7 and I'm kinda loving it. It runs full android, is made to be an mp3 player, but operates more like a phone without the phone parts. It has Wi-Fi and Bluetooth, but apparently has no location services, which is inconvenient if you want navigation, but great for privacy. It even has a camera.
They have non android mp3 players too if you want something more simple.