You can probably change the font in your favourite writing app to something with gratuitos serifs and retro charm, but it still won't come as close to recreating the feel of working on an antique typewriter as The Amazing Type-Writer app does.
For two bucks you'll be getting "...the latest in mobile pneumatic tubes technology with the highest-quality digital micro-swingarms available..." that allows you to reposition the carriage anywhere on screen, stamping over the misaligned and grungy characters you've already typed. Adding to the old-timey effect is the use of a simulated, highly textured mimeograph card stock which makes your notes, emails, musings and manifestos look like they're up for appraisal on The Antiques Roadshow. Your works can be published to an online gallery that's also accessible through the app, letting you download and annotate other user's creation. Or they can be emailed to grandparents, historians and the family of the person you're holding ransom. The only request we have is an iPad version so we can really get down to work. [The Amazing Type-Writer via Cool Hunting]