Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

 What: Shares of GPS technologist Garmin (NASDAQ:GRMN) plunged as much as 11% on Thursday after its current-quarter and full-year outlook disappointed Wall Street.

So what: Garmin shares have slumped over the past year on concerns over declining operating margins, and its second-quarter guidance -- EPS of $0.70-$0.72 on revenue of $770 million-$775 million versus the consensus of $0.89 and $773 million -- suggests that the pressure isn't letting up anytime soon. The company has needed to turn to new areas for growth such as fitness and outdoor activities amid the relentless threat from smartphone navigation apps, but those markets are proving just as difficult to crack. Specifically, intense competition from the likes of FitBit (NYSE:FIT) are forcing Garmin to price and promote more aggressively.

Now what: Management now sees full-year adjusted EPS of $2.65, down from its prior view of $3.10, but reaffirmed its revenue outlook of about $2.9 billion. "[T]he current competitive environment in the fitness market necessitates more aggressive pricing with higher advertising expenses," said President and CEO Cliff Pemble. "We are revising our full year outlook to reflect the dynamics we face in the current operating environment." Given Garmin's cash-rich balance sheet, juicy 4%-plus dividend yield, and other still-attractive growth opportunities, however, those short-term concerns might be providing patient Fools with a solid long-term income opportunity.

Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.