while it's possible to send image to glass in a timeline card, it doesn't look like it's possible to to the opposite (take a picture and upload it).
If I'm correct, this operation would be performed as a user action in the mirror APIs (like SHARE, REPLY, NAVIGATE), but I don't see any camera related function.
While you can't add a user action to take a photo directly from one of your timeline cards, you can register a Contact and Subscription to receive photos.
When the user takes a photo using the normal camera function of Glass, they can then SHARE the photo with your Contact and you will get a notification at the endpoint you specified in the Subscription.
See the following URLs as reference:
