=== Common steps ===
  * Cafe signs up
  * Cafe registers their foursquare/gowalla/google-buzz location
  * Cafe creates coupon

=== Plan A ===
  * User follows coupon bot.
    * con: requires user to know about coupon service
  * Coupon bot listens to followees for checkins
  * coupon bot sends message user with coupon

=== Plan B ===
  * Coupon bot listens to registered locations.
  * Coupon bot tweets with user's twitter handle and coupon

=== API Research ===

PDX Airport most popular checkin spot in portland. The checkins for the last 3 hours are exposed.

curl -u login:password http://api.foursquare.com/v1/venue?vid=35132

  <checkins>
    <checkin>
      <id>38869851</id>
      <created>Wed, 05 May 10 21:44:31 +0000</created>
      <timezone>America/Los_Angeles</timezone>
      <ismayor>true</ismayor>
      <user>
        <id>554xxx</id>
        <firstname>Angela</firstname>
        <lastname>D.</lastname>
        <photo>
          http://playfoursquare.s3.amazonaws.com/userpix_thumbs/IJRHQLWB5XXX.jpg
        </photo>
        <gender>female</gender>
      </user>
    </checkin>

The bot could have a foursquare account, and poll locations for which coupons apply.
Messaging that person with the coupon is the next hurdle. Need a mechanism for 
reaching them, foursquare doesnt seem to have one. Also it could feel spammy to
get notified at random when checking in.

$ curl -u login:password http://api.foursquare.com/v1/user?uid=554xxx
  <user>
    <id>554XXX</id>
    <firstname>Angela</firstname>
    <lastname>D.</lastname>
    <photo>
      http://playfoursquare.s3.amazonaws.com/userpix_thumbs/IJRHQLWBWGXXXX.jpg
    </photo>
    <gender>female</gender>
    <twitter>hertwittername</twitter>
    <facebook>12345</facebook>
  </user>

Even though we are not foursquare friends, the contact information is exposed. Most conviently
the twitter handle is exposed. A twitter account for this same bot could public-tweeet
@user you've got a $1 off coupon at store X for the next 15 minutes! Any good twitter
client will pick up that tweet in search.