Overall I think its pretty safe but keep in mind a paper wallet is of course way more secure, with a mobile its maybe pretty secure but it still can be hacked.
True, any Sophisticated equipment that we use there is definitely a gap to hackers, as well as for the wallet in a mobile phone. There must be a gap that could be searched by the hacker, I hope if you did do a cell phone inside the BTC storage, do not use the mobile phone to open a site that is not yet known.
Im using my mobile phone where i store my wallet and its pretty safe i dont see people claim that there mobile wallet is beinh hack not mention those hook by phising sites maybe it depends really on users how they handle their wallet tonbe safe