To clarify, it'll probably be a small miracle if the 1000mAh battery in the token lasts a full year...probably more like 6 months is a realistic lifespan for the token absent a battery replacement.
Realistically only a certain subset of the population needs to be tracked (cost-wise).
The ethical concerns with a tag that goes in your pocket (or similar) are more obvious but come the end of the pandemic you can throw it in the sea whereas once the technology exists in the phones you can't trust the government not to keep it in some form.
Given the amount of processing power available to a state, and the amount of data collectable from a smartphone, it's getting increasingly possible to have a system like (in principle - not sonar or graphical but powerful correlations of sensor data from static WiFi hotspots and similar) that shown in The Dark Knight. Unfortunately no one will have the spine to say no.
2. First amendment rights do not apply in an emergency
3. Don't compare covid19 to terrorism
4. Keep calm and carry on working from home
The same thing that stops companies from doing it continously and selling that data to the government, companies, bounty hounters, and ad sellers... I don't know what it is actually.