GSM 02.07 MS requirements
The GSM 02.07 specification (Version 7.1.0 Release 1998) lists a table of required and optional features of MS (mobile stations):
1.1 Display of Called Number M* 1.2 Indication of Call Progress Signals M* 1.3 Country/PLMN Indication M* 1.4 Country/PLMN Selection M 1.5 Keypad O (note 1) 1.6 IMEI M 1.7 Short Message M (note 4) 1.8 Short Message Overflow Indication M 1.9 DTE/DCE Interface O 1.10 ISDN "S" Interface O 1.11 International Access Function ("+" key) O (note 1) 1.12 Service Indicator M* 1.13 Autocalling restriction capabilities (note 2) 1.14 Emergency Calls capabilities M (note 3) 1.15 Dual Tone Multi Frequency function (DTMF) M (note 5) 1.16 Subscription Identity Management M 1.17 On/Off switch O 1.18 Subaddress O 1.19 Support of Encryption A5/1 and A5/2 M 1.20 Short Message Service Cell Broadcast M 1.21 Short Message Service Cell Broadcast DRX O 1.22 Service Provider Indication O 1.23 Support of the extended SMS CB channel O 1.24 Support of Additional Call Set-up MMI Procedures O 1.25 Network Identity and Timezone O 1.26 Ciphering Indicator M* 1.27 Network's indication of alerting in the MS O (NI Alert in MS) 1.28 Network initiated Mobile Originated connection O 1.29 Support of Localised Service Area O 1.30 Support of GPRS Encryption M (note 6) * Mandatory where a human interface is provided, i.e. may be in-appropriate for MS driven by external equipment. NOTE 1: The physical means of entering the characters 0-9, +, * and # may be keypad, voice input device, DTE or others, but it is mandatory that there shall be the means to enter this information. NOTE 2: MTs with capabilities for Autocalling, or to which call initiating equipment can be connected via the "R" or "S" interface, shall restrict repeated call attempts according to the procedures described in annex A. NOTE 3: Emergency calls shall be possible according to Teleservice 12 (see GSM 02.03  and GSM 02.30 ). This feature is only required to be provided by ME supporting Telephony. NOTE 4: Support of reception by the ME and storage of SMS MT in the SIM is mandatory, but its display is optional. Reception and storage of a message shall be indicated by the MS. NOTE 5: The use of DTMF is only mandatory when the speech teleservice is being used or during the speech phase of alternate speech/data and alternate speech/facsimile teleservices. NOTE 6: The implementation of GPRS encryption algorithm is mandatory for terminals supporting GPRS.
GTA01 implementation of [required] features
So how do we make sure we follow the mandatory requirements?
1.1 Display of Called Number
No problem here.
1.2 Indication of Call Progress Signals
This basically means that the user has to be informed about call initiated, other party ringing, busy, etc. Those audible signals are handled by the TI Calypso.
NOTE: Call progress indicators are described in GSM 02.40 
1.3 Country/PLMN Indication
We need to display the country and the currently selected network operator, as well as the list of available other operators. No problem here.
NOTE: The indication is described in GSM 02.30 .
1.4 Country/PLMN Selection
We need to support operator selection. No problem here. Has to comply with GSM 02.11 .
In TI Calypso.
1.7 Short Message
We need to support SMS 'properly', i.e. display it to the user, and acknowledge reception to the GSM network. Sending, too ;)
1.8 Short Message Overflow Indication
The user has to be told if his SMS memory overflows.
1.11 International access function
The user can use the "+" to generate the international access code. We should support this function. All of us travel way too much :-)
1.12 Service Indicator
We need to indicate sufficient signal strength and whether we're registered. This is done via the dockapp.
1.13 Autocalling restriction capabilities
I suppose this has already been implemented in the TI Calypso GSM firmware, since otherwise it in itself would not be GSM compliant.
1.14 Emergency Calls capabilities
Has to be implemented according to Teleservice 12 (see GSM 02.03  and GSM 02.30 ). Need to check those requirements!
1.15 Dual Tone Multi Frequency function (DTMF)
We need to be able to initiate DTMF in accordance with specifications GSM 02.03  and GSM 03.14 . This will put some additional requirements on both the dialler application and the GSM library/daemon infrastructure, since the DTMF tones are not actually transmitted as tones on the voice channel, but actually signalled as messages through the GSM network into the MSC (Mobile Switching Centre), which then creates the tones into to the voice channel.
1.16 Subscription Identity Management
No problem. This just says the we need to support SIM cards in their 'normal' way.
1.19 Support of Encryption A5/1 and A5/2
1.20 Short Message Service Cell Broadcast
We need to support receiving SMS Cell Broadcast. Interestingly, the requirement doesn't say we need to actually support displaying them :) Reception is supposedly handled within TI Calypso. Anyway, we should display them.
NOTE: The short message service cell broadcast teleservice is described in specification GSM 02.03 .
1.21 Short Message Service Cell Broadcast DRX
Some battery power saving mode for not listening to all cell broadcasts. TODO: Check whether TI Calypso supports this, and how we configure it. It's optional. But we care about power saving!
1.26 Ciphering Indicator
We need to support displaying whether any cipher (A5/...) is active, or whether the voice call is currently unencrypted. We also need to support restriction of this feature by the SIM module.
TODO: This will probably be another dockapp.
1.30 Support of GPRS Encryption
TI Calypso does that for us.