This app will send a text with the device's current GPS coordinates once per hour or two hours depending on which option you choose. If the phone or tablet's GPS is enabled, you'll know exactly where they are, and if not, the device will still provide a location based on the nearest cell phone tower or wi-fi hotspot. Since you receive the coordinates as a text message, you can copy the message and paste it directly into an app like Google Maps to see the location on a map.
Please note that this app is not intended to be 'sneaky' beyond it running automatically any time the phone/tablet reboots and sending out SMS texts in the background. The notifications will be visible in their texting 'conversation' with the phone number entered into the app. However, if you own the phone or tablet, you decide what apps are loaded. An EULA must be accepted before the app will run.