Watchman unit comes with the standard features. Additional features require subscription (per unit). Here is the cost information:
Subscription at $1.99/mon or $17.99/year
BuyOut at $44.99. BuyOut option offers all the same features (for life) with 1-time payment for the life of the Watchman. Please note that BuyOut is not transferrable. You may purchase Watchman along with BuyOut (instead of adding it later) and price is discounted.