Hi ,
Greetings from MobiInfo, i have read your requirement and i have worked on a similar product where user can get some service based on their location, its not for taxi but for some other service.
I can easily change , extend the existing app to suit your exact requirements , i have following ready :
1. android app
2. iPhone app
3. backend
I don't have a windows phone app but i can definitely get that done for you.
If you are interested please do let me know i can arrange a demo asap, i can promise you best work will be delivered to you in best cost.
FYI the cost and timelines mentioned are just to get in touch with you once i have the exact requirement i will propose the exact time and cost.
Regards,