The most important thing to remember when speaking of demons is what their purpose is--to lead people away from trusting in Jesus. Sometimes they do this deliberately and obviously, such as by tempting a person to curse God or commit sin. On other occasions, they might work more deceptively in quite the opposite manner--by leading a person to be moral or religious, but to rely on their morality or religiosity instead of the sacrifice of Jesus to receive God's blessing.
Regarding the specific case of digital communication being the medium for demonic activity, I would not rule it out, but I imagine the mechanism is slightly different than many would imagine. So, for example, it seems unlikely that a demon would possess a digital device or communicate directly with a person through it. However, it is highly likely that a demon would tempt a person to misuse a digital device in a way that would lead people away from Jesus.
An excellent example of this would be internet pornography or similarly inappropriate digital conversations. These would be perfect illustrations of the sort of thing a demonic force would love to have a person become entrenched in, and I have heard anecdotal evidence that many (men especially) have experienced demonic encounters that are directly or indirectly connected to habitual inappropriate uses of the internet. Obviously, this is just one of many ways in which they might tempt a person to sin by misusing technology, and the particular temptation might vary from person to person, manifesting in things such as habitual electronic gambling or neglect of one’s duties as a parent or employee in favor of wasteful internet use.
To summarize, it is entirely possible that a demon would use the TV, internet, or other forms of technology as a means to lead a person into something that will serve as an obstacle between them and Jesus. The best way to discern what one is experiencing in a particular circumstance would be to find a competent, Biblical, and trustworthy pastor in order to describe the problem in detail and seek his guidance. Because situations like this are so individual that no generic response will be able to do justice to the situation, personally involved pastoral care is the best resource.