Is there any way to monitor a cell phone without the person knowing?

It was horrible and very upsetting to find some unusual private sms messages on my husband's cell phone. I've never spied on him, but now my trust on him is completely broken. I need something affordable or free that can be installed on his phone without him knowing. Please help, I need proof whether he's being honest.

---

› See More: Is there any way to monitor a cell phone without the person knowing?

iKeyMonitor Mobile Spy Key logger - Run in stealth, invisibly SPY.

• Spy on websites visited
• Spy on SMS, WhatsApp Msg
• Spy on Keystrokes, Passwords
• Send the logs to you by Email/FTP
• Spy on Facebook Msg, Skype, IM+, Kik, Viber... and more...

For iPhone, iPad, iPod Touch: Download in "Cydia" for Free - 100% FULL Functional !

For Android, BlackBerry, Windows Phone, Symbian: Get Mobile Spy - Cell Phone Spy !