Hi,
For telnet, the command is "who" as follows:
ASA-5510-8x# who
0: x.x.10.10
For checking the privilege of the user, the command is "show curpriv"
ASA-5510-8x# sh curpriv
Username : aaaa
Current privilege level : 15
Current Mode/s : P_PRIV
ASA-5510-8x#
For console, since there is only one console port, at a time time there cant be more than one user connected via console.
HTH
Ashu