Whatever your problem is, it is not solved by knowing whether HR opened your email.
Really, there is no difference between HR ignoring your email by not opening it, or opening it and then doing nothing. Knowing which of these scenarios is occuring doesn't better equip you for a response. If someone hasn't responded in a reasonable amount of time, a reminder is appropriate, whether the email has been opened or not.
Furthermore, trying to track/monitor others' actions rather than trusting co-workers to do their jobs will be seen as adversarial and suspicious behavior. If discovered, this would look bad.
In short, don't do it.
Note: I assume you refer to something like hidden pixel email tracking. Email receipt functionality such as that found in Outlook is fairly innocuous and probably not going to cause concern if you use it...but I still don't really find it useful, for the reasons given here.