## 2 Materials and Methods
### Experimental Protocol
#### 2.3.1 Baseline Assessment Phase  
The following assessments were conducted by a trained member of the study staff: the Fugl-Meyer Assessment of Upper Extremity Sensorimotor Impairment (FM-UE [36]) sections A through D, which yield a total motor function score up to 66 possible points; the FM-UE Section H, which yields a total sensation score ranging up to 12 possible points; and right and left-handed grip strength using a JAMAR hand grip dynamometer [37]. After clinical testing, the study staff demonstrated the system and its nominal use. During this demonstration, we verified that all participants were able to feel the cues on at least one of the two arms. 3.2 IRF Feasibility Testing Phase: Progressive-Challenge Cue Activity Program and Passive Activity Monitoring  
Study personnel met briefly (i.e., typically \(<\) 5 min) with each participant twice per day in the IRF. Each morning, participants were instructed to wear both devices on their wrists and to keep the paired cell phone within proximity (about 25 ft) for a total of 8 h. Within  
Figure 2: _Souvenir_ comprises: two MetamotionR+ wearable activity monitors housed in silicone bands and worn on each wrist, an inexpensive Android smartphone with Bluetooth 5.0 capability, and a custom smartphone app that manages activity scheduling and data storage. this 8 h activity monitoring period, three 30 min cued activity sessions were scheduled. In these sessions, the system continued to monitor arm activity while the MetaMotionR+ devices delivered haptic vibration cues every 30 s. Thus, each participant was to respond to a total of 180 cues each day. The cues prompted participants to complete one of three activities (Figure 3): (1) tap--the user simply draws their attention to the MI side by tapping their MI arm with their LI hand, (2) assist--the user guides their MI elbow through its full flexion and extension range of motion using their LI hand for support, or (3) independent--the user performs independent active elbow flexion and extension on their MI side without assistance from the LI arm and hand. All participants began the study by performing the Tap activity on Day 1. They progressed in difficulty on subsequent days at their own pace and with study team guidance. Participants completed a minimum of 1 day of an activity stage prior to progression. Written instructions and pictures describing each activity were offered to all participants. _Souvenir_'s smartphone application requires the user to input the start times for three 30 min cued activity sessions during times when the participant is expected to be idle (i.e., between therapy sessions and/or other appointments). Study staff reviewed therapy schedules with the participant and collaborated to determine suitable cued activity session times. Study staff encouraged participants to independently determine session times to maximize autonomy with the system. Participants were allowed to doff the devices prior to showering or other event of water submersion but were asked to don the devices again once their skin was completely dry. In addition, participants were encouraged to doff the devices if they caused excessive  
Figure 3: Progressive challenge exercise program ranging from easiest (tapping; top) to more challenging (independent; bottom): (1) tap—the user simply draws their attention to the MI side by tapping their MI arm with their LI hand, (2) assist—the user guides their MI elbow through its full flexion and extension range of motion using their LI hand for support, or (3) independent—the user performs independent active elbow flexion and extension on their MI side without assistance from the LI arm and hand [27]. Labels a through c indicate the temporal order of actions for each exercise. skin irritation or discomfort, if they interfered with rescheduled therapy sessions, or if they became an annoyance.