Image Services require ArcGIS Server, so that won't be an option for you.
Once you convert to TPK, it will just be tiles that don't necessarily remember specific information or values in your original raster data, so you won't be running analysis against this.
If any of the Spatial Analyst tools in ArcMap suit your need, you can create your own GPK and use local server to execute the GPK in your Runtime App. Here is a list of supported GP tools in Runtime Local Server geoprocessing tools support—ArcGIS Runtime SDK for Qt | ArcGIS for Developers
Like I said, our Quartz release will have native capabilities to read raster files, which will not require local server. Quartz release will also have some new spatial analysis tools built directly into the API, and line of sight is one of them. This will also not require local server and will run completely client side. This will ideally be the workflow you use once it is released, but for now, you can consider displaying rasters through local server and running your analysis with a GPK through local server.
Thanks,
Luke