They will require real-time video of you at any activity you list. VHS, digital, and film reels are accepted. Each frame must be signed by the contact person and notarized by a registered notary public.
Above have it right. For proof, all you'll need it the contact information for someone there. Sometimes you need to bend those rules a bit (ie, Mr. X died, but Mrs. Y worked in the office, so you'll put her instead - it's just simpler).