You may not need a tool. This procedure (posted by someone else originally) works for my V70:

Clearing the Service Indicator[V70/1999] posted by David Bernick on
Thursday, 29 July 1999, at 5:05 p.m.

The procedure for clearing the Service indicator on the S70 and the V70 is as follows:
1) Turn the Ignition switch to the #1 position (radio on)
2) depress and hold the Trip meter clear button. THis is not the trip meter included with the Travel computer, but the standard trip meter clear switch.
3) While holding the trip meter clear button, turn the ignition switch to the #2 position (marked as II on the ignition switch).
4) Hold the trip meter button in until the Service light flashes (about 10 seconds). The service required indicator is now cleared. Release the trip meter clear button (before 14 seconds has elapsed).
DONE!