This backpack-friendly speaker uses Bluetooth technology to wirelessly pump out music from connected phones, laptops, and MP3 players. Thanks to its built-in microphone, it pulls double duty as a speakerphone as well. And it’s on sale for just $39.99 right now through Groupon as part of their Black Friday deals! You’ll want to hurry up and grab this one before it’s all gone. It’s normal price is $129.99, so it’s definitely a great price here.