The Cycle Analyst is by far the most useful ebike accessory on the market. It's a handlebar mounted cycle computer that monitors all of your ebike functions in addition to recording your ride speed, distance and time. The most necessary feature is a highly accurate battery gage. The Analyst measures the number of amp hours used in your ride, so you know exactly how much you've used and how much you have left. Without it, you might use too much power and run out a few miles from home. Or you'll be overly conservative of your use and never come close to using the full battery. With the Cycle Analyst there is no guess work, you know every time. If you're planning to use your ebike close to the limit of it's range, then this is a critical component of your system.
Stand-alone Cycle Analyst with handlebar mounting hardware, universal spoke magnet, and detailed user manual.