Cost: Free for individuals; $4.99/month/user for the Business version.
Available on Android too? Yes
Voxer adds push-to-talk functionality to smartphones. With the Business version, large corporate teams can communicate one-on-one or in groups in real time. The messages sent via Voxer are both live and recorded, as opposed to typical messaging apps where the message is packed, recorded, and then sent. The Voxer Admin Portal allows company heads or team leads to manage all Voxer users in the company, split users into teams, and even track, via geo-tagging, where messages are being sent from.