Seriously.....you could consider
1. constraining the mobile handset between two angle iron brackets in T slots, with a wooden coffee stirrer at each end of the handset/bracket
2. secure the base of the handset to the table with a few beads of silicone to the machine table
This could kill 2 or more birds at once & provide a stable harm-free method of securing the devices accelerometers without damage to the restraining machine or device
Derek