smartphone wallet is fully dangerous,  I mean insecure. it is not danger that much for that app, but it is for the keyboard we use or any other 3rd party app.

explanation:   There have been over 10,000,00,00+ downloads of emoji keyboards, (actually: keyloggers, spyware disguised as friendly emoticon keyboards.)
So when you want to enter your wallet, you need to type full info and password of your account, in the main time keylogger is  sending these onfo to victim's server. so you got hacked easily.
 
also we install many 3rd party app like : QR code or bar code scanner these get permission to read our contact, read to call log or making call even audio recording sometime.


Remember, on android any app can spy on you.
For example: our favorite flashlight app (third party) spying on you while you take a picture of a QR code to scan a bitcoin address, etc.
So I think Android is more risky than iPhone. So be careful.

Some tips to protect your wallet on smartphone :

1: make  sure to Delete all the apps you don't use.
2: When using your wallet, make sure NO background apps running.
3: Don't use any risky third party apps- (make sure your app ONLY USE the PERMISSIONS they need to operate.nothing else)
4: keep locked your smartphone when you are not using it.-
5: don't run/use 3rd party keyboards.