Windows Insiders running the latest Development Branch build on their phones can now send and receive SMS and MMS messages directly from a Windows 10 PC when Skype on their Windows 10 Mobile phone is set as the default messaging app. To make Skype your default SMS app on your phone, launch Skype Preview and go to settings and select “Make Skype your default messaging app”. Then on your PC, launch Skype Preview and go to settings and select “Enable Skype on this device to sync my SMS messages”. You will be able to view new messages as they arrive and respond to messages from your computer. Send and receive texts, group messages, and photos all in one app with a single view of your SMS and Skype conversations.
For more details – see this blog post from the Skype Team!