Pebble recently shipped its new Pebble Time smartwatches to Kickstarter backers, but there was initially a big problem: its iOS app wasn't approved by Apple (NASDAQ:AAPL) on time.

Pebble blamed "quirks in the App Store submission process and rules" for causing the delay. With customers left without a way to sync their watches to their iPhones, Pebble asked customers to voice their concerns on Twitter via the #FreeOurPebbleTime hashtag. After that nudge, Apple approved the app, and Pebble thanked its customers for carrying "the torch across the finish line."

Many media outlets speculated that Apple delayed the approval to shield the Apple Watch from competition. Back in April, Apple rejected navigation app SeaNav US for mentioning Pebble support in its App Store description, which violated a guideline that prevented developers from highlighting competing platforms. Although a David vs. Goliath showdown has been averted for now, could Apple eventually see the Pebble Time as a threat?

Why Pebble Time could threaten Apple Watch

Pebble entered the smartwatch market long before Apple, back in 2013, after raising over $10 million in a Kickstarter campaign.

By the end of 2014, Pebble sold its one millionth smartwatch, despite facing stiff competition from Samsung (NASDAQOTH: SSNLF) and Android Wear rivals. Research firm Smartwatch Group estimates that Pebble claimed 7% of the global smartwatch market in 2014, putting it in third place behind Samsung (26%) and Lenovo (OTC:LNVG.Y)/Motorola (10%).

Pebble's watches are cheaper and are more focused on streamlined notifications and power efficiency than high-end smartwatches like the Apple Watch. The original Pebble Watch only costs $99, while the more fashionable Pebble Steel and Pebble Time both cost $199. Developers also offer apps for Pebble within the iTunes App Store and Google (NASDAQ:GOOG) (NASDAQ:GOOGL) Play.

The Pebble Time has a few advantages over the Apple Watch. It's compatible with both iOS and Android, lasts for a week on a single charge thanks to its e-ink display, is compatible with standard watch bands, and syncs with third-party fitness apps like Misfit. Users can upgrade the Pebble Time with modular "smartstraps" which add additional features like GPS, NFC, or a longer battery life.

Remember how Apple treated Fitbit

It might seem silly for Apple to fret over a tiny competitor like Pebble, but we should recall what happened to Fitbit last year.

For a long time, Fitbit's fitness trackers could be purchased in Apple Stores. But last October, Fitbit refused to connect its fitness tracker to Apple's HealthKit dashboard, presumably to preserve its own ecosystem. That same month, it unveiled the Surge, a fitness tracking smartwatch which appeared to be a pre-emptive strike on Apple Watch. Fitbit also introduced Charge, which resembles a Fitbit Flex with basic smartwatch features like alarms and caller ID.

Shortly afterwards, Apple stopped selling Fitbit products in online stores, and removed them from its brick-and-mortar locations in March. However, Apple didn't block new versions of Fitbit's iOS app from being approved. Fitbit is the market leader in fitness trackers, but it isn't a direct competitor to Apple Watch in the smartwatch category. Smartwatch Group estimates that Fitbit only controlled 6% of that market last year.

If Pebble continues widening its lead over Fitbit with new devices like Pebble Time, it'll be interesting to see if Apple will let it keep building its custom app ecosystem within iOS.

A potential warning for Google

Pebble is in the clear for now, but Google and its smartwatch partners might not be as lucky.

Google is reportedly "close to finishing the final technical details" on adding iOS support to Android Wear devices, but I doubt that Apple will simply let Google's partners lure away potential Apple Watch customers. Apple already aggressively tried to reduce Google's presence on iOS devices by launching Apple Maps and replacing Google Search with Bing as the default search for Siri and Spotlight.

Apple isn't preventing iOS users from buying Pebble Time, but it made its position pretty clear on competing wearables when it booted Fitbit out of its stores. Looking ahead, things could get tougher for companies which want to make iOS-compatible smartwatches that run their own proprietary apps.