1. A downhole completion system (200) comprising:
- a production casing (3) installed in a borehole (6), and
- an annular barrier system (100) to be expanded in an annulus (2) between the production casing and a wall (5) of a borehole (6) or another well tubular structure (3a) downhole for providing zone isolation between a first zone (101) having a first pressure (Pi) and a second zone (102) having a second pressure (P2) of the borehole, the annular barrier system comprising an annular barrier (1) comprising:

- a tubular meta! part (7) mounted as part of the production casing, the tubular metal part having an outer face (4),
- an expandable metal sleeve (8) surrounding the tubular metal part and having an inner sleeve face (9) facing the tubular metal part and an outer sleeve face (10) facing the wall of the borehole, each end (12, 13) of the expandable metal sleeve being connected with the tubular metal part, and
- an annular space (15) between the inner sleeve face of the expandable metal sleeve and the tubular metal part, the annular space having a space pressure (Ps),
wherein the annular barrier system further comprises a sensor device (16) which is in communication with the first zone and/or second zone, respectively, the sensor device being adapted to measure the first pressure of the first zone and/or the second pressure of the second zone for verifying the zone isolation.
2. A downhole completion system according to claim 1, wherein the sensor device comprises an acoustic transducer.
3. A downhole completion system according to claim 1, wherein the sensor device comprises a piezoelectric element.
4. A downhole completion system according to claim 1, wherein the sensor device comprises at least a first pressure sensor (17) for measuring the first and the second pressures.
5. A downhole completion system according to claim 4, wherein the sensor device comprises a control unit (18) for providing communication between the

first pressure sensor and the first zone or the first pressure sensor and the second zone.
6. A downhole completion system according to claim 4, wherein the first pressure sensor is in communication with the first zone and a second pressure sensor (36) is in communication with the second zone.
7. A downhole completion system according to any of the preceding claims, wherein the sensor device comprises a storage module (19), such as a memory, a recording unit or a CPU.
8. A downhole completion system according to any of the preceding claims, wherein the sensor device comprises a communication module (24).
9. A downhole completion system according to ciaim 8, wherein the communication module comprises an acoustic transducer,
10. A downhole completion system according to ciaim 9, wherein the acoustic transducer comprises a piezoelectric element.
11. A downhole completion system according to claim 8, wherein the communication module comprises an induction unit configured to charge the power supply.
12. A downhole completion system according to any of the preceding claims, wherein the sensor device comprises an additional sensor (41) adapted to measure at least one fluid property, the fluid property being e.g. capacitance, resistivity, flow rate, water content or temperature.
13. A downhole completion system according to claim 12, wherein the additional sensor is a flow rate sensor, a capacitance sensor, a resistivity sensor, an acoustic sensor, a temperature sensor or a strain gauge.

14. A verification method for verifying zone isolation between a first zone (101)
having a first pressure (Pi) and a second zone (102) having a second pressure
(P2) of the borehole, the method comprising the steps of:
- expanding an annular barrier system (100) according to any of the ciaims 1-11 for providing the zone isolation between the first zone having the first pressure and the second zone having the second pressure,
- increasing the first pressure,
- measuring the first increased pressure and the second pressure, and
- performing an isolation check by comparing the increased first pressure with the second pressure.
15. A monitoring method for monitoring a condition of a weli (103), comprising
the steps of:
- expanding an annular barrier system (100) according to any of the ciaims 1-11 for providing zone isolation between a first zone (101) having a first pressure (Pi) and a second zone (102) having a second pressure (P2),
- measuring the first pressure,
- measuring the second pressure,
- repeating the steps of measuring the first and second pressures, and
- storing and/or transmitting the measured pressures.
16. A monitoring method according to claim 15, further comprising the steps
of:
- measuring a third pressure (Ps) inside the annular space,
- comparing the third pressure with the first pressure and/or the second pressure, and
- equalising the third pressure with the first pressure or with the second pressure.