Can I use wireless sensors with my VISTA 21iP?

Yes, it's possible for a Honeywell VISTA-21iP to use wireless sensors and its fairly simple! First, you will need to integrate a wireless receiver (aka RF receiver). You can choose between the following 2 options:

1. Install a keypad with a built-in RF module: Honeywell 6160RF or Honeywell 6150RF. The benefit of going with a keypad with an integrated RF receiver is that you get more capabilities out of your purchase. If you do not already have an alphanumeric keypad for programming, the 6160RF is your best choice due to its ability to program zones, serve as a keypad to arm/disarm and receive signals from as many wireless zones as your system will support. The 6150RF is a great choice if you already have an alphanumeric keypad for programming but you want to upgrade a secondary keypad (or add a new keypad) with support for up to 16 wireless zones. Both keypads that have an integrated wireless receiver must be hard wired to your alarm control panel using a standard 4 conductor cable - 2 for power and 2 for power. Also, it is imperative to note that only these keypads are capable of receiving wireless signals. The 6160, 6160V, 6150, and 6150V do NOT serve this function. Another advantage of using a 6150RF or 6160RF keypad is that they have an integrated wireless receiver and wireless transmitter so that they work with the wireless 5828 and 5828V keypads. The wireless keypads are bi-directional, meaning they can request status FROM the system and send commands TO the system, and they do not work with a standalone wireless receiver even if you have the 5800TM transmitter module installed.
2. Install a standalone wireless receiver: Honeywell 5881ENL (8 zones), Honeywell 5881ENM (16 zones), Honeywell 5881ENH (unlimited), Honeywell 5881ENHC (commercial fire & burglary), Honeywell 5883H (transceiver module). To choose the right receiver for you, you will need to determine how many wireless zones you plan on using. If you are unsure, it is best to play it safe and go with the receivers that are "unlimited". Unlimited in this case truly means that you are unlimited by the receiver but limited to the amount of available wireless zones that your alarm control panel supports. The VISTA-21iP supports up to 40 wireless zones assuming there are no more than 8 hard wired to the panel. If you do have more than 8 wired zones, you will need to subtract each zone beyond the original 8 to determine how many of the available 40 wireless zones are leftover to be used. These standalone receivers are great if you already have an alphanumeric keypad for programming and you don't plan to ever install wireless keypads.

Once you determine which wireless receiver best fits your VISTA-21iP, it is recommended to consider the wireless range of the furthest wireless sensor placement. The standard range for most of the Honeywell 5800 series wireless device is 200 feet (nominal) to the nearest RF receiver. The Honeywell 5800RP wireless repeater can double that range up to 400 feet assuming that you place the device approximately 200 feet from the closest receiver.