Writing a paper on a smartphone implementation of previous work Three months ago, I submitted a paper in an IEEE conference. The paper described a method to detect 'X' in images and a method to recover detected 'X' areas.

Now we want to show the performance and results of such an application on an android smartphone. For this, we have implemented the same detection method that we proposed earlier, however, we have also borrowed ideas from some other papers for a different recovery method (the recovery method proposed earlier was computationally expensive). 

To summarise, the present work differs from our previous work in following aspects:


First work to demonstrate detection and recovery of 'X' in an
android smartphone.
A new recovery method, but which it is inspired from other's work.


Does it make a good paper for publishing in a conference like: ICPR?
Stepping away from the details of your particular study, what you are more generally asking about is the distinction between studies of theory and of practice.  

The first paper you speak of introduces a method and demonstrates that it can work, but does not characterize its performance.  The second paper would then be characterizing its performance in a particular environment of interest.  From a scientific perspective, that is certainly a contribution of new knowledge (even if incremental).

To determine whether it is of sufficient interest to be published, you need to focus on the question of motivation: who will want to know about the performance and why?  What else will they need to know, such that you can create a complete and informative study.  The answers to these questions will depend critically on the precise details of your work and its context.