As far as I know, only the 3CX softphone and 3CX proxy server support the tunnel. 3CX Softphones developed for mobile devices may also be a possibility.
Theoretically any phone that does SIP properly supports the 3CX tunnel, having said that if you do mean ones that have implemented then there is no hardphone with this feature available, as its only a 3CX feature.
There are two ways to support your requirement. One is to use the 3CX tunnel proxy. Please see http://www.3cx.com/blog/releases/sip-proxy-manager/ The other is to use routers that support VPNs - such as Draytek 2820 routers. I have found both methods to work well. The advantage with the VPN is that you can use any phone.
VPN works well but it needs to be configured correctly, it is also NOT the supported means of connecting, but 3CX do help users in getting it up and running when they can.