The purpose of this clinical trial is to learn about the Tremor Retrainer smartphone application and Simplified Functional Movement Disorder Rating Scale in patients with functional tremor. The main questions the study aims to answer are:

1. Is the Tremor Retrainer application usable for patients and are there signs that it can help functional tremor?
2. Can a televideo administration of the Simplified Functional Movement Disorder Rating Scale give enough information to use this scale via televideo in future studies?

Following a one-week observation period, 20 subjects will complete the one-week four hour Tremor Retrainer smartphone protocol.

The study will consist of 4 in-person visits over 3-4 months and one televideo visit the same day as study visit 1.

For Objective 1, the investigators will evaluate mHealth Application Usability Questionnaire scores after subjects complete Tremor Retrainer protocol and compare Simplified Functional Movement Disorder Rating Scale (S-FMDRS) scores before (study visit 2) and after (study visits 3 and 4) intervention between groups.

For Objective 2, the investigators will evaluate which components can be scored after televideo administration of S-FMDRS and measure correlation between randomly-ordered sequential in-person and televideo S-FMDRS administration.

For Objective 3, the investigators will measure change and variability in S-FMDRS between study visit 1 and 2. S-FMDRS scoring will be completed via video review by a movement disorder neurologist blinded to timing of visit relative to treatment.

Inclusion Criteria:

1. Age 10 years and older, any gender, any race
2. Functional tremor as defined by Espay and Lang25, diagnosed by a movement disorders neurologist, involving at least 1 arm and ongoing at time of enrollment.
3. Access to internet and a laptop or tablet with a videocamera.
4. Informed consent obtained and signed
5. Subject understands study procedures and is able to comply with study procedures for duration of study

Exclusion Criteria:

1. Parkinson's disease, essential tremor, or other disorders causing involuntary movements in addition to functional tremor
2. Cognitive impairment with previously diagnosed intellectual disability (IQ<70) or dementia
3. Hearing impairment not addressed by hearing aids
4. Prior enrollment in clinical trial involving the Tremor Retrainer application

Anonymized participant data, including raw scores of outcome measures will be available for review.

Data anticipated to be available in 2026.

Anonymized participant data will be publicly available.