Fastwords are unsafe.
The alphabet has a size of 64.000 symbols (= words), and people will use 3-4 of them.
For 3 words there are just 262.144.000.000.000 different combinations to try. Renting a cluster of 30.000 machines for one hour costs less than 2k dollars. With such an attack you can try 5 trillion combinations per minute, which makes just max 52 minutes to crack such a password.<p>Mobile security can be achieved with LastPass for example, a password manager.
This can generate a password for you that is 20 chars long, with an alphabet of more than 70 symbols.
If we assume 70 symbols and just 10 of those in a password, then we already have 2.824.752.490.000.000.000 combinations, which is 10.775 times more secure than the fastwords example. So instead of cracking one hour, with a good 10 char password that includes symbols, uppercase and lowercase and digits, it would take around 416 days to crack a short mobile password, and it would cost millions.