Sentence:  [I]f an innovation has reached the maturity stage of the product life-cycle, then perhaps its functionality will be developed to provide a ‘<WSD>bolt-on</WSD>', with the core of the innovation remaining essentially the same. A classic example of a sustained innovation is the mobile phone, where functionality is increased by adding on extra capabilities, such as video, Internet acss, GPS tracking systems, music, and email. 
Meaning of the word marked with <WSD> tags:  A functionality or service that can be added to an existing arrangement or plan (for example, a mobile telephone subscription).