I have been riding cabs that have drivers with their own smartphone mounted on their glass. I saw the app flyer, also available in the cab, and immediately downloaded it. I've been using GrabTaxi ever since. I've tried EasyTaxi too but have not successfully booked any cab through it. The number of cabs linked to the app is probably few.
So far, I have no problem with GrabTaxi. You just have to register. For Metro Manila, you'll have to pay additional Php75 on top of your metered fare. For Cebu, it's an additional Php25 only. For this year, though, booking fee is free. :)
Now, I feel more confident traveling alone. I am assured that anywhere I go, I can grab a cab whenever I need one.
The app is easy to use. You just have to enter your pickup point and destination. You can use your location services for pickup point. In case you fail to see or meet your cab driver, you can call the driver too. Here are some screenshots using the app.
You can read more about this app at their website.