To get a list of ActiveSync Devices:

2010:

 

Get-ActiveSyncDevice -ResultSize Unlimited | Select-Object UserDisplayName, Name, DeviceUserAgent | Export-Csv C:\Temp\ActiveSyncDevices.csv
 
Exch2007:

 

Get-Mailbox | ForEach {Get-ActiveSyncDeviceStatistics -Mailbox:$_.Identity} | ft DisplayName, Devicetype, DeviceUserAgent, LastSuccessSync

  

Get ActiveSync information for specific user:
 
Get-ActiveSyncDeviceStatistics -Mailbox blye | ft DeviceType, DeviceUserAgent, LastSuccessSync