Bluetooth, the most common way for people to connect wireless headsets to their phones may not be as secure as you think. It is true that modern Bluetooth devices have improved in security but even the latest versions of Bluetooth still have security issues.
Many of the security concerns stem from a bluetooth device utilising low energy transmissions (LE) a feature used to maximise battery life. Unfortunatly this same feature opens vulnrabilities potentially allowing for eavesdropping on conversations by unauthorised parties. LE is a feature that the end user cannot turn off in LE configured devices.
It is important to note then that standard commercial Bluetooth headsets are not a good choice when dealing with highly-sensitive transmissions.
There are of course advantages to the current commercial Bluetooth technology as devices using LE tend to be lighter and smaller and therefore more comfortable to wear as well as richer in features. Manufactures therefore are naturally responding to the popularity of LE devices with consumers. This trade-off however is an important factor to consider and if security is a high priority then consumers should be aware before their purchase.
What to do if security is the top priority
Popular commercial choices may not be appropriate but there are some alternatives
Stay with Bluetooth - but look for a device that does not utilise LE or a device that charges using motion. As most Bluetooth headsets are in motion during use this should not be a problem for battery life.
Try Near Field magnetic induction - this technology offers a Bluetooth like experience with both improved battery life and improved security.