The ever-growing popularity of the iPhone has also seen the rise of some very successful apps, such as Instagram and Snapchat, worth $1 billion and $19 billion respectively. Now, as anticipation for the Apple Watch grows, developers want to know if they will be able to let their creative juices flow for the new device and make a ‘killer app’.

Markiyan Matsekh, product manager at software engineering firm Eleks, a company that is working on an Apple Watch app that will let users control Tesla Model S cars, is not confident, according to a Reuters report.

While good apps are essential to the success of the Apple Watch, Apple has blocked features like the gyroscope and accelerometer on the development kit and it is not possible to test all functions on the watch simulator.

Matsekh thinks the “limitations are discouraging” and apps need to be designed specifically for the watch, “not trying to take a phone app and cram it into a watch.”

However, app designer Mark Rabo sees the limitations as a challenge and is making an app that ties notes to calendars. One of its uses is that the watch will know when the user is walking into a meeting and pull up relevant notes.

Around 40 apps are listed on Apple’s website following the unveiling of the watch on Monday and it has said “thousands” more are in the pipeline.

The ones showcased so far are mostly extensions of services like Uber, American Airlines and Twitter.

One reason for this could be that “people are playing it pretty safe and right now just extending their application,” according to Ryan Taylor of Normative Design, who believes that once the watch is released, it will be easier to develop for.

Apple wants to “get people to think of apps differently than an iPhone app. That cultural shift is taking a little bit more time and that’s OK,” he said.

Apple Watch will be available from 24 April in nine markets and the line has been split into three collections: Apple Watch Sport, Apple Watch, and Apple Watch Edition.