My rear view windscreen mirror fell off, what do I stick it back on with?

Also, left dangling is a GPS unit, can I sync this with my phone somehow?

Cheers

Mirror adhesive

No comment on the GPS/Phone question . . . they don't belong in cars in my opinion

Tried 3 tips of Glue, all rubbish, waiting for a suction mirror from eBay. Cheaper than all the glue I bought

*types

Before you stick it back on, make sure the glass and the mirror are perfectly clean and degreased. Use white spirit. Then get a double sided mirror pad from any decent auto supplies to fix it back on. With traffic cameras on the lorries, we also put a tiny blob of super glue in the centre of the pad as back up. No fallers yet!