If you live and die through HDMI, then you might have heard a few stories (maybe experienced it yourself) about HDMI damage on your DSLR. This little achilles heel in DSLR workflow when using LCD monitors or EVF solutions can cost you big repair bills. Zacuto introduces a new HDMI lock (requires a zacuto plate to mount) called the Pincher. Not the cheapest solution, but it's almost the only one out there. Found at the Zacuto website, or a few dollars cheaper at B&H.
Zactuo HDMI Lock - Pincher
Or as some others have pointed out in the comments, the new TrusMT DSLR cage has HDMI locking options found here.
TrusMT DSLR Cage Ultimate with HDMI Locking