Sensor-based interactive art… That's a tall order. I don't have any real recommendations for it. “Chiyoda Arts 3331” (http://www.3331.jp/en/) next to Akihabara is not very interactive but quite artsy.
Apart from Akihabara, I definitely recommend spending a day in Odaiba, a tourist spot located on a reclaimed-land island in Tokyo Bay. There's a lot to do there:
One neat way to get to Odaiba is to take the Water Bus after spending the morning touring the old temple at Asakusa. If you're lucky (well, lucky if you like anime) you might get the “Himiko”. https://en.wikipedia.org/wiki/Tokyo_Cruise_Ship
For weekend spots I recommend being prepared for Sunday, which is when school is out and places will be crowded. If you like fashion or people-watching, the cool places to go would be:
Other artsy places:
You might (depending on your battery life/wifi) also want to spend some time with the recommendations from reddit: http://www.reddit.com/r/japan/comments/bvxaw/rjapan_information_hub/
Also: try the yakiniku and yakitori. Unless you're vegetarian.