I'm not sute if it's legal to use an app that monitors wallets (not trends) after the General Data Protection Regulation (EU) 2016/679 ("GDPR"), being in force. A lawyer could enlighten us on the matter. 
Hmm, I didn't even think that this may be a problem. Yeah, I think we could use some help from a lawyer. It would be very sad if it was an illegal thing to do. Thanks for pointing this out!