Saw this offer listed on my AmEx PRG. Curb is a taxi hailing app that is offered 65 U.S. cities, including New York City, Boston, Philadelphia, Chicago, Los Angeles, Las Vegas, Miami, and Washington,DC.
If offers dont show up on the standard AmEx website, check the older version page [americanexpress.com]
. Sometimes it may appear there.
This link [americanexpress.com]
should take you to the page to download on iOS or Android