Two types
Indoor cycling bikes vs air bikes
Indoor cycling (spin) bikes
A weighted or magnetic flywheel, a road-bike position and a power meter that reports watts, so you can train to structured sessions and track output. The six Spinning bikes here are all connected: Pace ($399) and Edge ($599) as entry models, Aero ($799) and Spinner Elite ($999) in the middle, Elite Power ($1,399) and the studio-grade Chrono Power ($3,695) at the top. All carry a 1-year warranty.
Air bike
A fan provides resistance that rises with effort, and moving handlebars work the upper body at the same time. Built for intervals and conditioning rather than long rides. The SFE Air Bike with dual moving arms, performance monitor and heavy-duty steel frame ($699).