You no longer need to hang around an Echo speaker to make free calls and messages with Alexa. As of now, you can use Alexa to place calls (including video calls) and send messages from Android tablets, iPads and of course Amazon's own Fire models. How easy it is depends on the device. It's easiest on the Fire HD 10, where you only have to ask Alexa to get in touch; other Alexa-ready Fire tablets require that you tap the home button first. And for everyone else, you'll have to open the Alexa app.
As usual, you don't need a tablet or Echo speaker to receive calls -- you just need the Alexa app. Amazon's Drop In feature also works between tablets and other Echo devices in your home, so you can use your tablet to ask someone a question when they're on the other end of the house. Effectively, Amazon is turning your slate into an intercom.