SpotOn Sleep/Wake Timer for Spotify lets you set a timer to fall asleep and wake up to your favorite tracks, albums and playlists.

Fall asleep and wake up to your favorite music
• Play any track, playlist and album from Spotify
• Slowly fade-out music at night and fade-in in the morning
• Use it on your phone or tablet
• Play music on other devices using Spotify Connect

To be added later (as optional)
• Weather forecast
• Low battery warning

...And much more. This is a testing beta so please be patient and send feedback and issues.
From version SpotOn - Sleep & Wake Timer for Spotify 0.1.70 beta:
Sleep timer playback is now done by the Spotify app, which means you can now enjoy all features of it, like Spotify Connect etc.
Wake option will follow soon.
Fixed search
Wake tab can be opened first now
Added sleep timer for Spotify
All versions