With this you can do the equivalent of AI-box. Moreover, using a screen you could be able to - among other things - induce epileptic seizure in some people, and you could definitely start broadcasting radio transmissions (as demonstrated with http://www.erikyyy.de/tempest/, which turns a CRT screen into AM radio playing arbitrary MP3s). I'll leave it to your imagination what an AI could do with that.

Basically you need to assume that (superhuman) AI will utilize any available side channel to further its goals. And there's a lot it could do with even a simplest of them. The lesson of today's technology that many miss is that you can do pretty much everything and every system can be exploited in thousands of more or less elaborate ways. We don't see them often because there is usually an easy and cheap method we stick to. We don't see "pretty much everything" being done, because it's usually too expensive to care. But if someone needs it, it can be done.

See also: side-channel attacks, hacker-style practical jokes.