A prospective, open-label, multi-center pilot study designed to evaluate the safety and effectiveness of the Felix system in the relief of upper limb tremors in adults with essential tremor and Parkinson's disease.

Inclusion Criteria:

1. At least 18 years of age.

2. Willing to provide written, informed consent to participate in the study.

3. For subjects with essential tremor (ET):

   1. A clinical diagnosis of ET.
   2. For either upper limb, a tremor severity score of 2 or higher as measured by one of the TETRAS items and a total score of 6 or higher across all TETRAS tasks.

4. For subjects with Parkinson's disease (PD):

   1. A clinical diagnosis of PD (MDS-PD criteria).
   2. A tremor score of 2 or higher on MDS-UPDRS question 3.15 (postural tremor) or 3.16 (kinetic tremor), OR
   3. A rest tremor score of 2 or higher on MDS-UPDRS question 3.17 (rest tremor amplitude) in one upper extremity and a score of 2 or higher on MDS-UPDRS question 3.18 (constancy of tremor).

5. Stable dosage of any medication, if applicable, for 30 days prior to study entry.

6. Familiar with operating a touch-screen smartphone and connecting to Wi-Fi internet at home.

7. If necessary, have a dedicated caregiver to help with study required activities, such as putting on the study device, etc.

8. Willing to comply with study protocol requirements including:

   1. Remaining on a stable dosage of current medications, if applicable, during the course of the study.
   2. Remaining on stable caffeine consumption, if applicable, during the course of t the study.
   3. No alcohol consumption on the day before a study visit.

Exclusion Criteria:

1. Prior limb amputation or any known symptomatic peripheral neuropathy condition of the involved upper extremity.
2. Any current drug or alcohol abuse.
3. Current unstable epileptic conditions with a seizure within 6 months of study entry.
4. Pregnant or nursing subjects and those who plan pregnancy during the course of the study.
5. Swollen, infected, inflamed areas, or skin eruptions, open wounds, or cancerous lesions of skin at the stimulation site.
6. Known allergy to adhesives.
7. History of Alzheimer's disease or dementia (Montreal Cognitive Assessment (MoCA)≤19).
8. Botulinum Toxin injection for hand tremor within 4 months prior to study enrollment.
9. Subject is currently participating or has participated in another interventional clinical trial in the last 30 days which may confound the results of this study, unless approved by the Sponsor.
10. Subject is unable to communicate with the investigator and staff.
11. Any health condition that in the investigator's opinion should preclude participation in this study.

From enrollment until end of follow-up, up to 10 days