It depends. Apple TV supports MP4 playback encoded with H.264 or MPEG-4 and AAC audio. If you have a file that's not encoded this way, then it won't work and you'll have to perform additional conversion.
The iSmartViewPro application records to MP4 and the files are stored internally. Firstly, try to play the file as it is and if it's not working, then use a converter to properly change it to play on Apple TV.
Converters: http://software.informer.com/search/apple+tv+video+converter
