I can not right away tell you the use cases of this procedure, but felt interesting. You can know the password entered through Get-Credential cmdlet.
$mycredentials = Get-Credential
[Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($mycredential.Password))
I got this from http://www.roelvanlisdonk.nl/?p=1150
Happy Learning..,
Sitaram Pamarthi