Uber is no stranger to using grassroots campaigns to push for pro-ridesharing regulation, but it just took things one step further: it's turning its app into a political activism tool. If you live in St. Louis, you now have an UberLetters option that sends old-school paper mail to the Metropolitan Taxicab Commission in hopes that it will allow the lower-cost UberX tier in the city. Once you've written your plea, you hail an Uber car that drops it off for free. It's an unusual move that will only last for a day (you have until 4PM on July 7th to act), but the company argues that these makeshift couriers are virtually necessary. The MTC only accepts public comments through fax or physical mail, so Uber couldn't just ask supporters to email their feedback.