Startup Idea : Offline app for calling a Taxi/Uber when abroad

Problem: When abroad you may not have roaming so you can't find taxi numbers to call, nor would you be able to get an Uber car.The idea for calling a taxi may be to have an app that contains an offline database of crowd-sourced taxi numbers from everywhere around the world. The user would be positioned by GPS and the app would show the local taxi numbers that the user could just call. In order to reduce language barriers, in some places the user may instead send an SMS to the taxi company with the current address and ask for a car in the local language, with the SMS template also crowdsourced the same way.For Uber, the application would instead send an SMS to a predefined number, also with the current GPS position and address. There would be a web service that receives and handles those SMS messages, where the user's Uber profile would have to be defined, and it would somehow intermediate an Uber call for that user.