Fitness wearable maker Fitbit had a forgettable end to 2017. The year was being billed as a transition period, but its long-awaited entry into the world of smartwatches -- the Ionic -- failed to deliver during its holiday shopping season debut. Now, 2018 will extend Fitbit's attempted rebound, and the company didn't waste much time in admitting last year's effort wasn't good enough.Two new lower-cost devices just became available for pre-order and are expected to begin shipping in April and May.Fitbit's two new wearables, the Versa and the Ace, carry lower price points than previous models.