Technically, EHS technology is used with the 'old-style' RJ-9 interface... but we get what you mean. Maybe...
On many USB adapter connected wireless headsets, you 'should' be able to use the button on the USB headset to answer, hang up calls a la EHS. If it is a Bluetooth connection to the adapter, then do what SteveInWA suggests and pair directly with the OBi1062 or OBiBT in the OBi1032/1022. Otherwise, if it is not working, let us know what make and model you are using and we will consider supporting this in a future firmware release.
Also, be sure to upgrade your OBi IP phone with the latest firmware (***6) as we have made improvements to the USB headset audio quality, recently. [v5.0.6 (Build 4176EX)]
Wired USB headsets are working great, generally.
If this answer does not jibe with your question, please let us know and we'll readdress.