It was the Davinci Tool. I ordered it from Amazon. I ordered the combo pack with came with a Firm and an Extra Firm version. The Firm is the better of the two as it has a little more give. If you get both, start with the Firm and eventually you can use the Extra Firm when you get used to using it.

The physical therapist I worked with used his fingers like a stand on my neck while I laid on my back and it immediately felt great. This device can be placed on three different sides, but the side the works the best is the Scalloped Edge. It is angled to match your nuchal ridge and the curvature of your skull.

When you move your head slightly in the direction as if you're looking up-down-right-left it will work out those muscles. As those relax, you can slightly lift and set down your head in different positions and it will crack a few cervical vertebrae. The pressure release is great and those muscles let go and those headaches subside.

I only recommend using it for about 5 minutes at first. Over time you can add longer periods. Eventually the need for it subsides.

Here's a pic and I'll follow with another reply with a link (as I'm not sure it will let me put a link in here).