Is that not the whole idea of this Grab/Uber thing ? Grab knows your location. You put your destination in and get a quote for going to that destination. That's how it seemed to work, although I've only really used it in the Philippines.
Actually, any time I book a taxi by phone, the first thing I do is check the fixed price before booking. If they put in words like "approximately" before the price, time to find another taxi company.