Today's Fitbit (FIT) - Get Report downgrade suggests inventory problems could plague the company and Apple (AAPL) - Get Report is emerging as the health play in the wearable technology space, says TheStreet's Jim Cramer. Pacific Crest has downgraded Fitbit to UNDERPERFORM, saying that Charge 2 is off to a slow start. Charge 2 is the company's flagship holiday product. The analyst also noted that he believes a large number of Fitbit owners stop using their devices within a few months, and that will make growth challenge. Fitbit's stock is down sharply this year.