Our club repeater is capable of two-tone paging. It uses a CAT-1000 controller.
Many moons ago in the mid 90's we had some Minitor I's pagers re-crystaled for the repeater.
With narrow-banding affecting all public safety channels there will be scads of Minitor III and IV pagers out there, hopefully for cheap.
The municipalities will likely upgrade to the Minitor V as it's narrow band capable.
While the III and IV are frequency programmable, the ones that will be coming out of service will mostly be the 151-159 MHz subband (B) versions. My model: A03KUS9239BC
Never fear, if you use the engineer login function of the pager programming software (in Minitor4 PPS ver 1.8.1), you can edit the engineering data, and change it to a 143-150 MHz (A) bandsplit. (the password is "Taipei")
As for the versions 159-167 and 167-174 I don't think these will lock down in the ham band.
This message thread on radioreference gives you good info in making your own Minitor Programmer. It gives you the pinout diagrams for the Minitors III, IV and V.
When I get a chance to test the sensitivity more in-depth I will edit this page with the results, and mods that I may deem necessary to improve the sensitivity.
Sensitivity is good. Near .4 uV
I haven't been able to track down a service manual, but this explains what to do if yours is not locking.
I have had success programming both M3 & M4's for ham freqs.