Hi,
Spanish translation sounds really exciting, but be prepared for a lot of work
I added some code changes and configuration options to make the Italian translation possible - things like number reading options and different inflections that are necessary in Italian but not English. Gianfranco worked very hard to get it all sounding as natural as he could. Hopefully some of these Italian language support changes would also be useful for a Spanish translation.
Like my glamorous assistant pointed out, install the app and take a look at the sounds it uses. The sound files don't have meaningful names - the folders they live in are used to identify the sounds. There are generally a few versions of each sound to give variety - this is optional (the app will work with only 1 version). Some of the sound files have magic names that indicate that the sound contains swearing, or that the sound can be used in conjunction with other sounds for personalisations (e.g. some sounds will be prefixed with "OK Jim, ...", some may be suffixed with "... please Jim"). Again, these are entirely optional.
Many phrases that the app uses are assembled from 2 or 3 individual sounds - e.g. "we think that", "Britton", "has gone off in", "La Source" - 4 separate sound files assembled into a sentence. The order of these is hard-coded so there are some challenges here.
I'll support you as much as I can but I do strongly recommend you take some time to understand the scale of the task and what the complications might be.