Flags - Recreate the 'poke' function
I created a test site with Flag and Views module enabled and so far, I could create a view to display users who have poked me. 

Create a new Flag to flag users. This don't have to be a global flag. Flag text could be "Poke" and unflag text could be "remove". 


  Users are presented with a list view of other users
  Users click the "poke" flag link on a single user



Create a view on users table
Add a new relationship: Flags: User. 
Uncheck "Include only flagged content "; Choose the poke flag; By: Current user. 

You will see a new field "Flags: Flag link". Add it. 


You will now get a view that shows users and a flag link to flag them. Modify the View as you wish. 
http://paste2.org/CGZshUFN


  Users then browse to /pokes/ and view all other people that have poked
  them


This is a really tricky part. 


Create a new View on users table. 
Add a new relationship: Flags: User flag. 
Uncheck "Include only flagged content "; Choose the poke flag; By: Any user. 

Add a new contextual filter: Flags: Content ID
Under contextual filter settings, choose the just-added relationship and set to user the current logged in user ID. 

Now we have access to a list of user IDs that has flagged the currently logged in user. 
Add a new relationship: Flags: User
Under this relationship's settings, check "require this relationship". 
Add a new field: User: name and choose the relationship created in step #7. 
Add a new relationship: Flags: User flag (yes, you are added one already in step 2 but go ahead). 
Under this relationship's settings, choose the the user relationship created at step #7. Uncheck "include only flagged content"; By: current user.

Add a new field: Flags: Flag link and choose the relationship created at step #10. 
http://paste2.org/tkWg99vp


Above step 12 will add the "flag back" type link that the user can see a list of users who have flagged the current user and a link to flag them back. 
You will need many Views template tweaks to adjust the wording of the View to suit your need.

Good luck!