Mobile usage statistics show the one thing that cannot be overlooked, which is the overwhelming usage of smartphones. According to the statistics, there are approximately 6.4 billion users of smartphones. Considering the world population, this rate of smart phone usage is more than 80%. Mobile development is the fastest prominent trend, although web development cannot be denied. However, the fact is that mobile platforms are considered cumbersome and complex when it comes to accomplishing requirement engineering processes, especially when mobile applications are combined with the Internet of Things (IoT). These complexities result in barriers to sustainable mobile development. The difficulty and differences occur due to various limitations, either that of mobile devices or others. Some of those from mobile devices include processor, battery, and touch screens, user experience in terms of touch screens, user context, and interactive behaviors. Other limitations include the difference in the software development lifecycle and the difference in the software development process due to inconsistency in user requirements with the aforementioned limited device capabilities. The target objective of this research is to investigate and identify all possible challenges related to mobile applications and connected mobile devices (IoT) while executing the requirement engineering process. This study can further the existing state of knowledge by contributing to the list of challenges faced in the requirement gathering process of mobile application development. Furthermore, it can also help practitioners, specifically those involved in the requirement gathering process, to carefully consider these challenges before executing the requirement engineering process.