I agree with you up to this point:
OMdev wrote: because there is no such alternative in market.
There are plenty of survey tools that offer an app to run their questionnaires offline, just have a look at store. As far as I know, SPSS offers an android app for their CAPI solution, Qualtrics has this, etc.
But we should look into this. For example, what sawtooth does for their offline CAPI is offering an EXE file to download on a computer and this is actually a webserver that runs just like the normal SSI tool, but locally. Then you need to import the survey file and later to export the datafiles. We could use a similar approach. Both as an exe file for desktop/notebook offline capi and as apk for mobile (tablet smartphone). For both solutions there is already a base. We actually have an exe package already, including limesurvey. What would be necessary to make it practical would be an easy way to import surveys (the normal way wouldn't work with most interviewers, even if it is not that complicated, we need already to be happy if they can install an exe file) and as OMdev said, we also have already apps that install a webserver on an android device. However, I am not sure how good a tablet or smartphone can handle the newer versions of Limesurvey, because they require more and more from the server (at least this is my feeling).
So what we would need to look at is actually these things:
1. Importing surveys easily (including templates and images of the survey)
2. Exporting surveys easily
3. Import surveys easily back on the server (problem could be the IDs here, we would need to make sure to know from where the interview came from - which interviewer, etc.). Ideally this would go directly into the database when there is a internet connection, so that the interviewer doesn't have to do anything. But this is probably just a good wish. I would already be happy when the results would come back as a file that can easily imported.