A computer-implemented method, comprising: receiving, at a computing device comprising an activity tracker, a user input to invoke performance of an activity by the computing device; identifying multiple portions of computer code associated with the activity, wherein each portion of computer code among the multiple portions of computer code is scheduled to be executed by the computing device at different times, wherein each portion of computer code among the multiple portions of computer code for the activity comprises a respective original portion of computer code; for each portion of computer code in at least a subset of the multiple portions of computer code for the activity: modifying, by a re-coding engine of the activity tracker, the portion of computer code to include (i) pre-work operations that are arranged to be executed before the respective original portion of computer code is executed, and (ii) post-work operations that are arranged to be executed after the respective original portion of computer code is executed; for each portion of computer code among the multiple portions of computer code associated with the activity: executing the respective portion of computer code, wherein executing the portion of computer code comprises executing the modified portion of computer code, including executing the pre-work operations for the portion of computer code, the respective original portion of computer code for the portion of computer code, and the post-work operations for the portion of computer code, recording data about the executing of the respective portion of computer code that indicates a time duration of the executing of the respective portion of computer code, and determining whether at least one subsequent portion of the computer code is also required to be executed to complete the activity; and outputting a total time to completion of the activity based at least in part on aggregating the recorded data about the executing of the multiple portions of computer code. receiving, at a computing device comprising an activity tracker, a user input to invoke performance of an activity by the computing device; identifying multiple portions of computer code associated with the activity, wherein each portion of computer code among the multiple portions of computer code is scheduled to be executed by the computing device at different times, wherein each portion of computer code among the multiple portions of computer code for the activity comprises a respective original portion of computer code; for each portion of computer code in at least a subset of the multiple portions of computer code for the activity: modifying, by a re-coding engine of the activity tracker, the portion of computer code to include (i) pre-work operations that are arranged to be executed before the respective original portion of computer code is executed, and (ii) post-work operations that are arranged to be executed after the respective original portion of computer code is executed; for each portion of computer code among the multiple portions of computer code associated with the activity: executing the respective portion of computer code, wherein executing the portion of computer code comprises executing the modified portion of computer code, including executing the pre-work operations for the portion of computer code, the respective original portion of computer code for the portion of computer code, and the post-work operations for the portion of computer code, recording data about the executing of the respective portion of computer code that indicates a time duration of the executing of the respective portion of computer code, and determining whether at least one subsequent portion of the computer code is also required to be executed to complete the activity; and executing the respective portion of computer code, wherein executing the portion of computer code comprises executing the modified portion of computer code, including executing the pre-work operations for the portion of computer code, the respective original portion of computer code for the portion of computer code, and the post-work operations for the portion of computer code, recording data about the executing of the respective portion of computer code that indicates a time duration of the executing of the respective portion of computer code, and determining whether at least one subsequent portion of the computer code is also required to be executed to complete the activity; and outputting a total time to completion of the activity based at least in part on aggregating the recorded data about the executing of the multiple portions of computer code.