Apologies for not replying sooner,
Just to go back to the initial request for thought and ideas on use of "smart" devices to measure vibration exposure. And perhaps to make my point from another perspective:
As we (and the HSE) know there are huge variations in vibration emission (thickness of material, type of material - wood, steel, concrete etc... pressure applied, condition of tool, condition of accessory - eg. worn grinding disc), as well as task duration or actual trigger time. The HSE expect, using best practice, an uncertainty of still around +/-20% or higher!
As such what is requested by the HSE is, and I quote "a reasonable estimate" of employees exposure. The "likely" level of vibration and duration of use/exposure. And to answer your previous question, yes I do personal measurements of exposure (even some under water!), usually 3 times per tool and on 3 separate users - in the case where the risk assessment estimates the risk for a group of employees all conducting a similar task or using the same tools.
The use and purpose of such "smart" devices or tool timers, in my opinion serves only to fill this gap in knowledge (or where there is significant uncertainty or variability) to make a reasonable risk assessment of the task / hazard. Level of emission and duration of use.
In absence of reliable manufacturer data (which is a lot better than it used to be, as manufacturers now have to present emission levels to the new standard, as recognised by the HSE on the old standard this could under-represent by as much as 50% - and the hse USED to recommend double the emission level - but no longer):
HSE state: "Please be aware: Please refer to page 6, 'Estimating exposure,' second paragraph - "However, if the only information available to you is the vibration emission declared in the equipment’s handbook, it may be safer to double this figure before using it for estimating daily exposures." - Due to the implementation (29/12/2009) of the Supply of Machinery (Safety) Regulations 2008, supplementary European Standards have been revised to help manufacturers provide information that can be used to estimate daily HAV exposure"
I would still recommend to measure the emission yourself, and use this in your risk assessment, than to implement a costly and questionable "smart" monitoring system (as above I am concerned how this measures the emission of the tool in relation to the point of conact with the hand) - which I say again, in most cases will only act as an expensive tool timer.
Personally, my risk assessments highlight maximum use times which are marked clearly on the tools. This is usually by a colour coding system, green indicating tool can be used all day and in combination with other green tools, amber no more than 4 hours per day, and red where a significant constraint applies. However there are only a few occasions where red is used, as the first priority after identifying a "red" tool is to look at alternative work methods or lower vibration alternatives.
I dont know if I have covered all points raised above, but I more than happy to discuss this further should anyone have any questions or comments. For example I have had experience managing a number of historical cases (stage 3+), targetted HSE inspectios on HAVS, reporting under RIDDOR of identified HAVS and a number of legal defence claims, the type of questions asked and the expected type of evidence required to be presented to successfully defend (again due to historic exposures - and not current practices).