You would declare an emergency because your gadgets fail?
You're kidding, right?.
I know this was intended for GPS only, but for others out there:
Last year on a night flight (short XC) I got a faint "wiff" of smoke in the cockpit. As I shed all non-essential electrical, my ALT enunciator lit up for a split second followed by a much larger amount of smoke entering the cockpit (I was now 10 miles to landing and over an interstate highway). I was able to get off a single "AC in distress, ALT failure, smoke in the cockpit 10 north inbound -as two CBP helos were practicing auto-rotations over the approach threshold). Within seconds of that ALT light and short radio transmit, my battery overloaded and all electrical was gone for good. The bolts holding the front and rear case of the ALT sheared, the ALT rotated on its bracket and the pulley froze (causing the smoke from the belt). My handheld was on the rear floor in my flight bag, but the headset adapter would have to be fished out (I didn't). On final, the helos didn't move and I had navaigate around them and land mid-field.
Lessons Learned:
1. Keep the headset adapter ON the handheld on night flights, not just in the bag close by.
2. Glad I had several of the hat lights available. Have an Iphone APP for lighting as well as a backup to the backups.
3. I had heard millions of times you'll have about 30-60 minutes once the ALT fails before the battery follows suit. Now am aware that the ALT may take it out simultaneously ... the battery didn't explode, but it was definitely fried.
4. Moderate smoke in the cockpit at night is NOT fun.
5. Glad I have a Halon fire extinguisher within reach if necessary.
EDIT: Probably should be #1 above
6. After an event like this, when you get home .... Your family is going to smell the event well before you get a chance to shower. If the spouse is skittish about flying, get cleaned up BEFORE heading home at a friends.