I posted this in response to another user asking this question, so will repost:
We did have plans for this from the very conception of Cachly. I have had an Apple Watch since they first came out, and most recently have the Series 2.
However, the watch doesn't provide enough API's and hardware to really make a good watch app for geocaching. For example, there is no compass in the watch, so trying to build a compass would still rely on holding your iPhone in hand.
Currently it does seem to be more of a novelty, but we are continuing to keep it on our feature list and hope to get it added in a future version.