This may sound crazy but it just might work.  I've been trying to choose an HRV or ERV for the house I'l be building in northern Michigan,  zone 6.   The HRV manufacturers all say I should use an HRV, even if they also make an ERV.  However one ERV maker, Renewaire says their units work fine in ANY climate, need no drain and have no defrost requirements, and recover more energy than an HRV can all appealing attributes.  Some of the manufacturers offer electronically comutated motors (ECM) which dramatically lower energy use.  Another feature I like.  Renewaire doesn't offer ECM in their residential size units but they do in 2 of the smaller commercial units rated at 450 CFM and !000CFM.  A 150 CFM unit is about the size my house would normally need.  Well I looked at the data sheet , spec etc for the Renewaire ECM units.  Amazingly the 450 moves 200 CFM against 0.2" wc resistance using only 46 watts, that's awesome!  Almost twice the cfm/watt of the next best available unit.  It's always possible to further reduce capacity by 'duty cycle" control for example 30 minutes./hour running is equivalent to 1/2 of 200CFM or 100 CFM.  Being a commercial unit it has gauge ports and a table of flow rates vs pressure differential across those ports and a control to vary the blower speed.  Then the really crazy idea occurred! OMG this thing is most of what's in a blower door test setup!  If one disconnected the outside air inlet and capped the duct to the outdoors, put a gauge port in the cap, hooked one manometer across the units gauge ports and another hooked up to measure the inside to outside pressure differential.  Turned the unit on, adjusted the unit's speed to have 50 pascal pressure difference between inside and outside the other manometer and table give the building leakage in CFM.  Presto a blower door test with the ERV  Well it'll work up to 500 CFM of leakage, above that it will not make the 50 pascal differential pressure.  In my case 500 CFM is 0.7 ACH, above where I want to be.    The cost of up sizing the ventilator and two manometers is less than a grand & I can seal & test forever! with a built in blower door!

Can it also adjust interior pressure to equal the outside pressure - ie, reduce in/ex filtration?
Would probably require two fans.

I think you would have to make a graph of motor current verses pressure in different situations to figure out how to get a proper reading. It is an interesting idea.

Mike,
    No need to do any graphing!   The manufacturer has a table of pressure readings, across the core to predict flow.   It's figure 1 in this"  http://www.renewaire.com/images/stories/Literature/ecm_manual.pdf

Jonr,  The unit is intended to be installed with balancing dampers which are used to provide either balanced pressure indoors & out or deliberate slight unbalance to guarantee a controlled infiltration or exfiltration when the ventilator is running.  This model has pressure ports that make these kinds of setups easy.  So the answer to your question is yes when it's running.