What would be simpler than returning them in a hash? ...oh yeah, returning them in a list! Here ya go.

void
tdSensor()
   CODE:
   {
      char protocol[_MAX_PROTOCOL_LEN + 1];
      char model[_MAX_MODEL_LEN + 1];
      int  id;
      int  dataTypes;

      int rv = tdSensor(
         protocol, sizeof(protocol),
         model, sizeof(model),
         &id,
         &dataTypes
      );

      if (rv != TELLSTICK_SUCCESS) {
         XSRETURN(0);
      }

      EXTEND(SP, 4);
      ST(0) = sv_2mortal(newSVpv(protocol, 0)));
      ST(1) = sv_2mortal(newSVpv(model, 0));
      ST(2) = sv_2mortal(newIV(id));
      ST(3) = sv_2mortal(newIV(dataTypes));
      XSRETURN(4);
   }
[download]

Usage:

use feature qw( say );

while (my ($protocol, $model, $id, $dataTypes) = tdSensor()) {
   say join ', ',
      "protocol: $protocol",
      "model: $model",
      "sensorId: $id",
      "dataTypes: $dataTypes";
}
[download]

Untested.