tracker

noun
1
a person who can find people or wild animals by following the marks that they leave on the ground
ردیاب, کسی که ردپا را دنبال می‌کند
2
a device that follows and records the movements of somebody/something
ردیاب, دستگاه تعقیب‌کننده
Electronic trackers show how far the animals range in search of food.
see also fitness tracker
3
an investment fund that aims to follow in value a stock marketindex or group of indexes
سرمایه‌گذاری شاخصی
Forget about fund managers and individual shares: choose an index tracker instead.