Aside from just getting a Hallmark card, you could sing a song and post it online to wish Happy Birthday. It will make the person happy regardless of his/her personal interests. If you’re not much of a singer, you could bring some of your friends with you and make a chorus. Just make sure there is at least one or two-person in the group who is good at singing so that he/she helps you guys to stay in tune.
Making video compiling pictures of you guys together would be a good way to wish someone Happy Birthday. It shows that you care for the person and made time for doing something special. Also, looking at the pictures would be a nice walk through the memory lane and might strengthen your bond. Make sure to put a beautiful song in the background. You could also put nice birthday messages on top of the pictures or write a letter that would run through the video.
Most people would wish someone Happy Birthday by calling them or sending a Hallmark card. Sending cards will never go out of style. But, it would show much more care and affection if the card is handmade. So, you could go through DIY card making videos available on YouTube and make a Birthday card by yourself. You could add some good pictures of you with the person and nice messages or even a hand-written letter. If you want to do something more, just send a chocolate box that the person loves with the card.