Known implementations for FHIRPath
- Java RI: In the FHIR build tooling at org.hl7.fhir.dstu3.utils.FHIRPathEngine
- Pascal RI:  - see the library
- .NET RI: https://github.com/ewoutkramer/fhir-net-api - the .NET api includes a FhirPath evaluator.
In addition, there is a Notepad++ FHIR Plugin that enables evaluation of FHIRPath expressions:
There is a test harness for FHIRPath here:
The CQL-to-ELM translator that is maintained as part of the tooling for Clinical Quality Language is incorporating FHIRPath as part of the 1.2 branch: