Note that an app for iOS and Android provide additional functionality. You can access your device's photo roll, so you can take a picture and use that as your annotated image; you can record video, add it to the image, and upload it directly to your Thinglink account.*
Thinglinks can also be a powerful way of demonstrating visual literacy as well. On a basic level, choosing an exclamation mark versus a shopping cart icon should be deliberate within the context of the information that pops out. After students are familiar with the site, push students to not just annotate with information, but intentionally decide icon placement in order to add another level of complexity and understanding. For example, in my Thinglink above, there was a reason I put Nirvana’s “In Bloom” video icon in the trees!
I caught up one of Mr. Nichols's classes near the end of the project, as the groups were presenting their finished products. The engagement was genuine; the "publication" of work was authentic; the sense of shared ownership and cooperative work was palpable; and the note-taking of the audience (along with their Q & A at the end of each presentation) showed there was true value in the content given. Once again, tech created a leadership opportunity for the students.
*Note 5/20/15: I added the info about how the Thinglink mobile apps work.