I really like units like the LG Tone headset. It hangs around your neck like a tiny yoke, and has a couple of earbuds that go up to your ears. You can use just one of them.

The LG is $40+ but I've seen knock-offs for as little as $10.

As a bonus they're great for listening to podcasts and such while mowing the lawn because they're some of the only BT headsets that you can put ear defenders on over them.