OMeR is described as 'is the printed music recognition add-on for Melody Assistant or Harmony Assistant' and is an app in the Audio & Music category. There are three alternatives to OMeR for Windows, Android, Android Tablet, iPad and iPhone. The best alternative is ScanScore. It's not free, so if you're looking for a free alternative, you could try PlayScore.
With ScanScore you can scan sheet music and have them played to you. For scanning, you can use a smartphone, a tablet or a conventional scanner. Via the MusicXML interface you can export your notes to almost any music program and edit them further.
Advanced music scanning and recognition OCR (OMR) software. PhotoScore is a music scanning program - the musical equivalent of a text OCR program. It is also able to convert PDF files to editable and playable notation.