These Sentry Cellphone and Music Ear Buds feature a built-in omni-directional microphone. 
Sentry Cellphone and Music Ear Buds:
Compatible with mobile phones, MP3, iPhone, Blackberry and more
Microphone: omni
Frequency: 20Hz-20kHz
Impedance: 32 ohms
Cord length: 4' (1.2m)
Plug type: 3.5mm
Drivers: 10mm
Adapter: 2.5mm
Max power: 50mW
Color: white