If you want to have an affair
Use a dumbphone. Although the phone companies' marketards would have you believe you'll never pull with one.
Google has decided that eavesdropping is a step too far for even Android's laissez-faire attitude to application vetting, and rejected such an app despite waving it through first time. Secret SMS Replicator was initially approved by Google and listed in the Android Marketplace, but Switched explains that 18 hours later the …
Until there is a "guest user" capability in handsets, sharing my phone is something i am LOATH to do. I fear that someone could run off with it. I fear that someone could scroll through my phone list if i turn my back. Someone could send messages in my name and ... well, you get the idea.
Newer, draconian phone theft laws should passed, too. Stealing someone's phone or phone and wallet should be viewed as a dangerous attempt to steal a person's identity. Stealing a phone often can yield MUCH more information and access than stealing a wallet alone could.
It's common sense. When you see on the news, celeb after celeb getting their sleazy sexting plastered on the tabloids, you'd think it'd clue people in - don't text message when you're screwing around.
Of course, that's common sense, which as y'all know is anything but common.