The wife suggests a "Wedding Day Emergency Kit"
Put in stuff like:
Breath mints
Small pack of deodorant
Tide bleach pen
Safety Pins
Bobby pins
Aspirin
Sewing kit
Band Aids
Small bar of chocolate (don't let it get on the dress!)
Tweezers
Lint Roller
etc.
etc.
Those were some she thought of, but if you google wedding day of emergency kit, you'll find a whole list of other items as well.
And add a little heartfelt note for her sealed for her to read the day of (I'm so happy for you, breathe, it'll be wonderful, you deserve this, etc. etc.)
If it fits her/you, a small bottle of alcohol (airplane sized).
Put it all in a cute little box, decorate it, done.