They're not popular yet because they're only made by small outfits rather than by companies with big factories, so most recliners cost more than regular bikes. You turn the motor on when you need it with a button on the handlebars. The motor is typically powered by a small lead-acid battery which you can recharge by plugging it into the wall. You can either buy a complete bike along with the motor, or you can just get the motor and attach it to your existing bike. Trikes are usually better than bikes for hauling large loads with a trailer.
Many trikes even have a cargo box built in, such as the one in the photo at right.
Wal-Mart in Bastrop also used to carry adult trikes, but I don't know if they still do. Trailers BOB trailers are quite popular. Check out BikeRoute's Comparison Table of various trailers . Web Guide Workbike.org is the definitive site for information on carrying loads by human power, all over the world. Check out an Austin-based tandem club .