Here is a way to use Garadget with Chamberlain Security 2+ openers. Such openers are incompatible with a contact output such as from a doorbell switch or Garadget (known as a ‘dry contact’ because there is no voltage provided by the doorbell switch or Garadget device), but there is an easy solution. This solution should apply to other openers that do not accept a dry contact input.
I purchased a new Chamberlain 3-button remote to overcome the fact that Chamberlain Security 2+ does not accept dry contact inputs. The remote does accept a dry contact input. Garadget supplies the dry contact input to the remote.
You can see in the sequence of photos that I soldered wires to the SW2 normally open terminals on the printed circuit board (you could use SW 1,2, or 4. SW3 is not recognized). I used a twisted pair from an old Cat 5 cable. I glued the wire to the PC board with hot glue so it would not flex and break off the connection. I could not find my small electronic soldering iron so I had to use a larger one and the soldering job is not very pretty. I set up Garadget according to instructions late one night, but when I went to bed apparently the server had not yet updated with my installation. There was a triangle with an exclamation mark superimposed over the garage door art. In the morning however the exclamation mark was gone and all seemed to be well on the workbench. I guess it just took some time at the server to update itself to this device. I physically installed everything in about 30 minutes. You can see the installation on the Chamberlain drive assembly in the photos.
I have enabled the Alexa app for Garadget and now have voice control over the garage door plus I can inquire about the status from any Alexa device in the house. I did not damage the new Chamberlain remote device so it can be used independently again someday just by clipping off the wires.
I highly recommend this solution to the problem of interfacing a dry contact output from Garadget with the Security 2+ system that Chamberlain has which does not recognize a dry contact. Whatever opener you have, if it will not accept a dry contact input such as from a doorbell switch, you can just buy one of their remote devices and parallel the output of Garadget with one of the push-button switches on the remote device.