Sipdroid

Sipdroid is an excellent VOIP tool for Android that lets you use your Internet data plan to make phone calls. The only inconvenience in the app is that it needs to be configured in a pretty complicated way, which can make most users take a step back.

The interface in Sipdroid, in fact, is so simple that you just have to insert the phone number you want to call, and you can start your phone call just like that. Nevertheless, in order to do that, you first have to go through the app's settings. And that's where things can get a bit more complicated.

You have to spend a good while setting up Sipdroid if you want to get the most out of the app, which is in fact a lot. Basically, you have to set up your SIP account and check that all the audio options are properly configured.

Sipdroid is a great alternative to other VoIP applications, and despite having a pretty ugly and excessively simple interface, it does the job perfectly.