Always start where you are with what you already have.
Check the documentation for the cell phones themselves, or contact the cell phone manufacturers you are targeting and ask them what their ICs are predisposed to. Otherwise, I recommend that you focus on Java, which was conceived and developed by Sun to sit on a variety of common electronic devices. However, Java is not simple or easy. It is an object-oriented language with a huge developer library. Microsoft COM might work well for this functionality, too.
It sounds like you prefer to develop your own application (for a commercial product perhaps?), so you may not want to survey products/apps that are already available on the market that do what you want, but that would be a fertile place to research, if only to compare what is available versus what you want to invent. Otherwise perhaps you could look at existing apps and get rights to modify them from the developer.