Encrypted Messenger app

The ISO 27001 certificate is not mandatory, but if you implement and certify it, you can give good image and warranty of information security to your customers, because this standard establishes requisites to manage the protection of the information.  Also the annex A of the ISO 27001 has a set of security controls related to the development (for example: access control to the source code, secure development environment, system security testing, etc), that maybe can be helpful for your business. 

If you want to know more information about the ISO 27001, please read this article “The basic logic of ISO 27001: How does information security work?” : https://advisera.com/27001academy/knowledgebase/the-basic-logic-of-iso-27001-how-does-information-security-work/