I use Smartlock 1.7E (you can find it searching here). Offers the incall/outcall locking. This is *exactly* the reason I use it.
It's a shame - WM6.5 has the ability to lock in-call automatically, because my Intrepid did it and it worked perfectly. For some reason Sprint/HTC dropped the ball on this 6.5 update.
I tried later versions of Smartlock. 2.0F doesn't play nice with the keyboard configurator, and 2.0E seemed to cause either memory or battery issues (I can't recall). 1.7E has been rock solid for me.