GTalkSMS or its owner don't and won't collect any data from your phone and cannot be responsible of data loss.
Personal data might be sent outside your phone (SMS, Photos, Files...) as it is the core feature of the application. So you need to be careful with which XMPP provider you're using.
GTalkSMS recommends to use a secure connection with your XMPP provider.

If you are concern with the privacy policy of your XMPP provider, please consult them.