One of the best uses for an SPL meter in an HT is balancing the channel levels. For this purpose absolute accuracy is not terribly important, repeatability is. The RS meter and most other meters are very repeatable. If you want high accuracy, you'll have to move up to a more expensive meter, like the Gold Line meters.
For spectrum analyzers, absolute SPL accuracy is not that important either, just relative levels. To be accurate for SPL measurements a PC or Pocket PC based RTA needs to be calibrated. Typically with an accurate, standards traceable, SPL meter.