Being able to "feel" electric/magnetic fields with your hands would be great. Not dissimilar to wifi sensing, but enough to be able to intuit what a circuit is doing just by observing/feeling it.

I also don't think that anyone's mentioned having a true internal clock. Some people can already wake up at a specific time of day just by wanting to - that'd be useful. Also for the ability to time things.

Lastly, while being able to detect neurotransmitter levels in your own brain would be great, being able to detect them in the brains of others would be even better. Kind of a toned-down empathic ability - you could tell who was stressed, who was happy, and so on by the amount of cortisol or dopamine in their brain.