For most performers that don't move around that much, your money is far better spent on something like the Rolls PM50s wired headphone amp. Has a Mic-thru so the performer can do a "more me" mix on their own. The PM351 is aimed at keyboard players, who much like drummers, don't benefit much from a wireless IEM.
The Rolls will sound wise outperform any budget wireless IEM out there. the PM50s is also battery powered and will last an entire gig. At under $60, it's a no brainer for several in the band.
For guitar players, if you do move, just tape a headphone extension cord to your guitar cord, and whoila! Mobility.