B&H Photo Video offers the Sony Wireless Bluetooth In-Ear Sports Headphones in Black, Red, or Blue, model no. MDR-XB50BS, for $39.99 with free shipping. That's $13 under our January mention and the lowest total price we've seen. (It's the best deal today by $10.) They feature up to 8.5 hours of playback per charge, built-in mic, sweat resistance, and Arc supporters.
Update: Specs corrected.