1. A wearable computing device comprising: a first sensor group configured to enable a user to input desired content; a second sensor group configured to detect user environment information including at least one of a user's activity state and environment situation at a present position of the user; a user information providing device configured to provide the user with one of an instruction for the user to take an action and collateral information for use in determining the action, said one of the instruction and the collateral information being provided for realizing both the input desired content which is input by the first sensor group and determined based on the user environment information detected by the second sensor group and a user activity support agent configured to produce information to be provided in the user information providing device based on both the input desired content input by the first sensor group and the user environment information detected by the second sensor group, and to provide one of the instruction and the collateral information, thereby supporting the user's activity, wherein the user activity support agent includes: a target detection evaluation module configured to set as a physical target destination, both the input desired content which is input by the first sensor group and the determined desired content which is determined based on the user environment information detected by the second sensor group, such that the target destination is set as a final step in a flow comprising a plurality of steps defining an action necessary for achieving the target destination, and to provide the user with information for confirming whether or not the target destination is desired by the user via the user information providing device based on the outputs from at least one of the first and second sensor groups; and an activity plan evaluation module configured to plan the target destination determined as the desired target destination based on the user's reaction evaluated by the target detection evaluation module in such a manner as to realize the target destination by an activity group of the steps included in the flow to reach the target destination, based on the user environment information detected by the second sensor group, and to provide the user with a set of navigation directions for achieving the target destination and information suggesting the activity group via the user information providing device to perform at least one of monitoring and evaluation of an achievement degree with respect to the user's reaction to the information based on the user environment information detected by the second sensor group, and also to provide the user with information indicating a result of said at least one of the monitoring and evaluation.