Apple’s upcoming wearable device, based on iOS, will run third-party applications and, furthermore, may come equipped with an App Store, according to two sources with knowledge of the new device. It is currently unclear if the App Store will be full-fledged, like on the iPhone and iPad, or if it will be a special section with in the iPhone App Store for apps that play nicely with the new wearable device.

A small handful of high-profile social network and services companies with apps on the iPhone and iPad App Store have already been seeded with a pre-release version of the Apple SDK (Software Development Kit) for wearables under strict non-disclosure agreements. One of the developers with access to the pre-release SDK is Facebook, according to a source. Facebook is also said to be finishing up work on an iOS 8-optimized version of its iPhone app with improved notifications. The social network is also experimenting with ways it can leverage the new Notification Center widget APIs.

The SDK was seeded “very recently” to these developers, and Apple likely wants to demonstrate some third-party wearable apps at Tuesday’s event, according to one source. Apple, in the past, has provided select developers with early versions of SDKs in order to boast new apps on the keynote stage. For example, several apps from companies like AOL were shown off with the first public demonstration of the iPhone SDK, fancy gaming and drawing apps were demonstrated alongside the first iPad in 2010, and the iPhone 4S’s dual-core A5 chip was launched alongside a graphics-intense video game…

The new Apple wearable will be released early next year, which will give developers of all kinds ample time to design, build, and polish their own apps by the time the new hardware actually hits the streets. The new SDK will likely have deep ties to iOS 8’s Extensions, HealthKit, and HomeKit APIs. Additionally, the Apple wearable device’s SDK will make good use of the new Continuity, Handoff, and Widgets features for iPhone users to be able to easily transfer content from the smartphone to the wearable and vice versa.

To be revealed on Tuesday, the wrist-worn Apple wearable will boast a fashionable appearance, but still function as a smart watch with fitness-centric features. Sources first revealed to us in January that the device includes a miniaturized system-on-a-chip to store a multitude of sensors ranging from sweat detectors to pulse readers to motion sensors. The device will also include new wireless sensors (including an NFC chip) to act as a conduit for Apple’s upcoming mobile payments platform.

Sources also said that a key component of the new device’s software will be mapping functionality that is reliant on the new sensors. Apple has assembled a group of fashion, fitnesspayments industry executives, and medical sensor experts over the past two years to create this device, and pre-event marketing seems to indicate that the watch could live up to the hype.