OK, I tried this a couple times today, with disappointing results. I was trying to use it to help me focus on a video lecture I was watching, but I found it pretty hard to maintain any sustained increase in my level of activation... even when I got it to spike temporarily, it would immediately start going down. Also, the fact that it read data from my fingers meant I couldn't use that hand to create spaced repetition cards. Overall, it served as way more of a distraction than an asset, and I don't think I noticed any focus benefits immediately afterwards when I stopped using it and restarted the video I was watching from the beginning.

It's conceivable that you could make this work through a gradual increase rather than sudden spiking, or configure the dial so that it would only start to make noise once your level of activation went below some threshold. I might experiment with those ideas in the future.

If you want increased alertness, there are other hacks in the thread for that, like D_Malik's ideas of blue-tinted glasses or spraying/splashing water on your face (and of course there's always caffeine etc.) Supposedly yawning also improves alertness.