Dear Shibu,

No, I don't believe there is currently an Italki app.  There used to be an Italki Messenger app, launched back in 2013, but I couldn't find it now.  More information in these threads:

http://www.italki.com/discussion/76221

http://blog.italki.com/?attachment_id=1010 ;

http://blog.italki.com/tag/italki-app/

I use Italki on my smartphone and their mobile version works really well (in my opinion).  

I hope that helps :)