Are there any GPS devices that can be tracked in real-time WITHOUT the use of a SIM card ? Or is there any possibility to track a GPS device which has lost the network signal ? Assuming they can both send and receive sms and mine has internet connection ? Something like every minute it checks, not need for a real time hard track but as good to know where to find her if she gets attacked. I want to develop an app for it
That's a little confusing: No SIM = no SMS. No network = no connection = no communication. GPS is only a receiver, it does not send. That leaves binoculars as only tracking method then – which, besides, even works with devices not featuring GPS. As long as visual contact is possible, at least ;)
Apart from that, I guess we've got an XY problem here: "good to know where to find her if she gets attacked" › How do you know she's attacked? GPS alone won't tell you.
Maybe you're rather after Personal Protection solutions. There are some featuring an "emergency button" – and others with a "dead man's switch": the former sends out an alert when pushed, the latter sends one if not pushed within a given interval. If such an app is good, it figures what means of communication is available – and can broadcast an distress signal by all of them: Sending out SMS and mails including the coordinates (GPS or network based, whatever is available), posting on Twitter/Facebook, and even initiating calls to 911 (or whatever number you tell it to use).
One such app would be Watch Over Me, including most of those features: Track-Me function, Dead-Man-Switch; Real-Time recording; Email/Facebook, and more (on subscription even more again). For alternatives, simply follow the link to my list :)
Your questions are a bit confused so I'll address what I think you're asking:
Many apps already exist that can "track" devices, even without a cell network. Airdroid and Lookout both come to mind but you can also do a search for any security apps that use a "find my phone" theft component.
True SMS (not over wifi) generally requires a SIM card. From wikipedia: "Though most SMS messages are mobile-to-mobile text messages, support for the service has expanded to include other mobile technologies, such as ANSI CDMA networks and Digital AMPS, as well as satellite and landline networks."
In order to be able to track the device, it must have one or more of the following
1. Mobile network (and SIM card if it is GSM or LTE capable CDMA). GPRS or better for internet tracking. Must be SMS capable for SMS tracking.
3. Ethernet (yes, android supports this)