Can I use a GPS or Distance Measuring Device system in the competition?

There are no competition rules prohibiting their usage. 2019 Rules of Golf allow the use of DMDs without the need for a Local Rule.  But, courses can implement local rules restricting their use, in which case the competition rules support the local rule.

Although the Rules of Golf allow the use of DMDs, players must ensure that the device they use complies with the restrictions in Rule 4.3a(1). Further Guidance can be found here from the R&A