We've recently added the ability to post trips to twitter. Here's a simple example:
To tweet your trip from Passenger app, tap the "share" button on the top right corner of the map, then tap on the twitter button in the share dialog. Passenger will generate your tweet out of the trip's data: travel mode, distance, duration and notes. Since notes include #tags, they are automatically parsed. A map with an overview of the entire trip is included in the tweet.
Here's how my example tweet appears on twitter
Posting trips on Twitter is available from Passenger iOS version 2.2.1, and coming soon to the Android app.