OK. What you want to do is create a circular ringed fence Location sensor (ringed fence / circular ringed fence). In principle, it is possible to determine if an Android is within a circle of a certain radius using the LocationSensor. In practice it probably is not possible to determine with certainty the person is within a relatively small diameter circle.
To determine if 'if someone want to attand...he have to go to place in a radius of office coordinate' is going to be a problem. Why?
- the gps will not work very well within an office building. Accuracy will be high values (indicative of the imprecision of the location determination). The gps will not know exactly where it is.
- the LocationSensor can only resolve, at best 2 meters. If the person is 2 meters inside the the ring fence, the app may indicate he/she is outside of the fence and he/she won't be able to send an sms. Why? Read about the LocationSensor property Accuracy for an explanation.
You can try the example and see what happens. Is the accuracy sufficient?
A better method of determining where a person is in an office would involve scanning a barcode. He/she scans the Barcode component to read coordinates posted in a QR code on a wall in the office. Scan the barcode; if the bar code scan result indicates the person is in the office, he/she can send the Text message using sms.