I need to come up with a pressure sensitive pad in the bottom of a gate mailbox to give status on a touchscreen in a home.

I can figure out the programming and wiring part, but any ideas on a pressure sensitive mat that would trigger on letters dropping on to it?

A trigger on the mail flap won't do for client

thats an awesome idea!

I would think a proximity sensor drilled in the bottom may work well

[Link: grainger.com]

what about a contact, stating that the door was opened

Well that's no good because that may mean someone just opened the door and/or the mailman took that days mail but delivered nothing :-)

Pressure sensing mats are common...the key will be finding one that is sensitive enough to notice the change when a single letter is in the box. Cool project...looking forward to how you accomplish this.

I'm not sure but at least these are cheap enough to play with:
[Link: uneotech.com]
and then use a ARDUINO (or COMPATIBLE) Microcomputer.

Put the contact on the door, and sell them a video camera to go inside the box.

Then they can not only see if there's mail, but see who sent it too?
"Why get the mail when it's just junk mail anyway?"

Sure it does.. it lets them know if someone, anyone has opened the door to the mailbox, where as the presure mat may not trigger if the post card is too light

I wouldn't think that not registering a postcard would be a dealbreaker.

Presumably this is being installed to let the client know when there is mail to get. Rare is the day I only get 1 or 2 pieces. Usually my mailbox is full of junk.

I'd say that if there was a day that there wasn't enough mail to measure, it would be corrected by the next day.

The other problem is how are you to distinguish between what is going out and what is coming in? Or is this a problem? I know in some areas here in Canada the mailboxes are incoming only (no big deal) but other areas are both.

Isn't there some kind of light sensor you could use (like a garage door safety sensor but smaller).

Maybe some kind of electric eye, with a beam to break.

This may do you

[Link: cardaccess-inc.com]

Simon beat me to it, I was going to suggest calling Card Access. They are my #1 place for those kinds of devices that you say "that's a cool idea, I wonder if anyone makes something to do that easily?"

That said, what about LED illumination inside, and a couple of photo sensors on the bottom?

Or this: three or four lever microswitches mounted on the floor, with a metal plate sitting on the levers. Adjust lever length to adjust spring tension, and change metal weight to change sensitivity. Wire em up in parallel, and you have a mechanical contact-closure sensor for mail! 

We once used a set of Pulnix mini photo electric beams inside the mailbox, when the mail came it blocked the beam and closed a set of contacts. Worked amazing.

[Link: SecurityStoreUSA.com]

Depending on how large the box is, you could use one of these:

[Link: enforcer.com.tw]

Put the reflector on the bottom and when mail is dropped on it blocking the photo beam, you get a dry contact closure.

+1 on the photo electric, plus you could rig up a contact closure sensor to the flag to see if the mail inside is outgoing or not.